[ANCHOR-355] Implement SEP-6 deposit (#1035)

This implements the SEP-6 `GET /deposit` endpoint _mostly_ according to
the sequence diagram from the PR.

Where the implementation deviates is how `CUSTOMER_UPDATED` anchor
events are structured. This implementation sends out 1 event whenever a
SEP-12 customer is updated instead of fanning them out a
`TRANSACTION_STATUS_CHANGED` event for each ongoing transaction
submitted by the customer. This was done to keep the scope of this
change small, but we can consider whether to move this into the platform
later.

api-schema/src/main/java/org/stellar/anchor/api/event/AnchorEvent.java

@@ -2,6 +2,7 @@
 
 import com.google.gson.annotations.SerializedName;
 import lombok.*;
+import org.stellar.anchor.api.platform.CustomerUpdatedResponse;
 import org.stellar.anchor.api.platform.GetQuoteResponse;
 import org.stellar.anchor.api.platform.GetTransactionResponse;
 
@@ -13,8 +14,7 @@
  *     Schema</a>
  */
 @Builder
-@Getter
-@Setter
+@Data
 @NoArgsConstructor
 @AllArgsConstructor
 public class AnchorEvent {
@@ -23,6 +23,7 @@ public class AnchorEvent {
   String sep;
   GetTransactionResponse transaction;
   GetQuoteResponse quote;
+  CustomerUpdatedResponse customer;
 
   public enum Type {
     @SerializedName("transaction_created")
@@ -32,7 +33,9 @@ public enum Type {
     @SerializedName("transaction_error")
     TRANSACTION_ERROR("transaction_error"),
     @SerializedName("quote_created")
-    QUOTE_CREATED("quote_created");
+    QUOTE_CREATED("quote_created"),
+    @SerializedName("customer_updated")
+    CUSTOMER_UPDATED("customer_updated");
 
     public final String type;
 

api-schema/src/main/java/org/stellar/anchor/api/platform/CustomerUpdatedResponse.java

@@ -0,0 +1,14 @@
+package org.stellar.anchor.api.platform;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class CustomerUpdatedResponse {
+  String id;
+}

api-schema/src/main/java/org/stellar/anchor/api/platform/PlatformTransactionData.java

@@ -4,6 +4,7 @@
 import com.google.gson.annotations.SerializedName;
 import java.time.Instant;
 import java.util.List;
+import java.util.Map;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -86,7 +87,23 @@ public class PlatformTransactionData {
   Customers customers;
   StellarId creator;
 
+  @SerializedName("required_info_message")
+  String requiredInfoMessage;
+
+  @SerializedName("required_info_updates")
+  List<String> requiredInfoUpdates;
+
+  @SerializedName("required_customer_info_message")
+  String requiredCustomerInfoMessage;
+
+  @SerializedName("required_customer_info_updates")
+  List<String> requiredCustomerInfoUpdates;
+
+  Map<String, InstructionField> instructions;
+
   public enum Sep {
+    @SerializedName("6")
+    SEP_6(6),
     @SuppressWarnings("unused")
     @SerializedName("24")
     SEP_24(24),

api-schema/src/main/java/org/stellar/anchor/api/sep/sep6/GetDepositRequest.java

@@ -0,0 +1,68 @@
+package org.stellar.anchor.api.sep.sep6;
+
+import com.google.gson.annotations.SerializedName;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NonNull;
+
+/**
+ * The request body of the GET /deposit endpoint.
+ *
+ * @see <a href="">GET /deposit</a>
+ */
+@Builder
+@Data
+public class GetDepositRequest {
+  /** The asset code of the asset to deposit. */
+  @NonNull
+  @SerializedName("asset_code")
+  String assetCode;
+
+  /** The Stellar account ID of the user to deposit to. */
+  @NonNull String account;
+
+  /** The memo type to use for the deposit. */
+  @SerializedName("memo_type")
+  String memoType;
+
+  /** The memo to use for the deposit. */
+  String memo;
+
+  /** Email address of depositor. Currently, ignored. */
+  @SerializedName("email_address")
+  String emailAddress;
+
+  /** Type of deposit. */
+  @NonNull String type;
+
+  /** Name of wallet to deposit to. Currently, ignored. */
+  @SerializedName("wallet_name")
+  String walletName;
+
+  /**
+   * Anchor should link to this when notifying the user that the transaction has completed.
+   * Currently, ignored
+   */
+  @SerializedName("wallet_url")
+  String walletUrl;
+
+  /**
+   * Defaults to en if not specified or if the specified language is not supported. Currently,
+   * ignored.
+   */
+  String lang;
+
+  /** The amount to deposit. */
+  @NonNull String amount;
+
+  /** The ISO 3166-1 alpha-3 code of the user's current address. */
+  @SerializedName("country_code")
+  String countryCode;
+
+  /**
+   * Whether the client supports receiving deposit transactions as a claimable balance. Currently,
+   * unsupported.
+   */
+  @SerializedName("claimable_balances_supported")
+  Boolean claimableBalancesSupported;
+}

api-schema/src/main/java/org/stellar/anchor/api/sep/sep6/GetDepositResponse.java

@@ -0,0 +1,26 @@
+package org.stellar.anchor.api.sep.sep6;
+
+import lombok.Builder;
+import lombok.Data;
+
+/**
+ * The response to the GET /deposit endpoint.
+ *
+ * @see <a
+ *     href="https://github.com/stellar/stellar-protocol/blob/master/ecosystem/sep-0006.md#response">GET
+ *     /deposit response</a>
+ */
+@Builder
+@Data
+public class GetDepositResponse {
+  /**
+   * Terse but complete instructions for how to deposit the asset.
+   *
+   * <p>Anchor Platform does not support synchronous deposit flows, so this field will never contain
+   * real instructions.
+   */
+  String how;
+
+  /** The anchor's ID for this deposit. */
+  String id;
+}

api-schema/src/main/java/org/stellar/anchor/api/sep/sep6/Sep6Transaction.java

@@ -1,8 +1,11 @@
 package org.stellar.anchor.api.sep.sep6;
 
 import com.google.gson.annotations.SerializedName;
+import java.util.List;
+import java.util.Map;
 import lombok.Builder;
 import lombok.Data;
+import org.stellar.anchor.api.shared.InstructionField;
 import org.stellar.anchor.api.shared.Refunds;
 
 @Data
@@ -77,7 +80,14 @@ public class Sep6Transaction {
   @SerializedName("required_info_message")
   String requiredInfoMessage;
 
-  // TODO: use a more structured type
   @SerializedName("required_info_updates")
-  String requiredInfoUpdates;
+  List<String> requiredInfoUpdates;
+
+  @SerializedName("required_customer_info_message")
+  String requiredCustomerInfoMessage;
+
+  @SerializedName("required_customer_info_updates")
+  List<String> requiredCustomerInfoUpdates;
+
+  Map<String, InstructionField> instructions;
 }

api-schema/src/main/java/org/stellar/anchor/api/shared/InstructionField.java

@@ -0,0 +1,15 @@
+package org.stellar.anchor.api.shared;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@Builder
+@AllArgsConstructor
+@NoArgsConstructor
+public class InstructionField {
+  String value;
+  String description;
+}

core/src/main/java/org/stellar/anchor/sep12/Sep12Service.java

@@ -8,14 +8,18 @@
 import io.micrometer.core.instrument.Metrics;
 import java.util.Objects;
 import java.util.Set;
+import java.util.UUID;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import org.jetbrains.annotations.NotNull;
 import org.stellar.anchor.api.callback.*;
+import org.stellar.anchor.api.event.AnchorEvent;
 import org.stellar.anchor.api.exception.*;
+import org.stellar.anchor.api.platform.CustomerUpdatedResponse;
 import org.stellar.anchor.api.sep.sep12.*;
 import org.stellar.anchor.asset.AssetService;
 import org.stellar.anchor.auth.Sep10Jwt;
+import org.stellar.anchor.event.EventService;
 import org.stellar.anchor.util.Log;
 import org.stellar.anchor.util.MemoHelper;
 import org.stellar.sdk.xdr.MemoType;
@@ -31,7 +35,12 @@ public class Sep12Service {
 
   private final Set<String> knownTypes;
 
-  public Sep12Service(CustomerIntegration customerIntegration, AssetService assetService) {
+  private final EventService.Session eventSession;
+
+  public Sep12Service(
+      CustomerIntegration customerIntegration,
+      AssetService assetService,
+      EventService eventService) {
     this.customerIntegration = customerIntegration;
     Stream<String> receiverTypes =
         assetService.listAllAssets().stream()
@@ -41,7 +50,9 @@ public Sep12Service(CustomerIntegration customerIntegration, AssetService assetS
         assetService.listAllAssets().stream()
             .filter(x -> x.getSep31() != null)
             .flatMap(x -> x.getSep31().getSep12().getSender().getTypes().keySet().stream());
-    knownTypes = Stream.concat(receiverTypes, senderTypes).collect(Collectors.toSet());
+    this.knownTypes = Stream.concat(receiverTypes, senderTypes).collect(Collectors.toSet());
+    this.eventSession =
+        eventService.createSession(this.getClass().getName(), EventService.EventQueue.TRANSACTION);
 
     Log.info("Sep12Service initialized.");
   }
@@ -69,11 +80,22 @@ public Sep12PutCustomerResponse putCustomer(Sep10Jwt token, Sep12PutCustomerRequ
     if (request.getAccount() == null && token.getAccount() != null) {
       request.setAccount(token.getAccount());
     }
-    Sep12PutCustomerResponse response =
-        PutCustomerResponse.to(customerIntegration.putCustomer(PutCustomerRequest.from(request)));
+
+    PutCustomerResponse response =
+        customerIntegration.putCustomer(PutCustomerRequest.from(request));
+
+    // Only publish event if the customer was updated.
+    eventSession.publish(
+        AnchorEvent.builder()
+            .id(UUID.randomUUID().toString())
+            .sep("12")
+            .type(AnchorEvent.Type.CUSTOMER_UPDATED)
+            .customer(CustomerUpdatedResponse.builder().id(response.getId()).build())
+            .build());
+
     // increment counter
     sep12PutCustomerCounter.increment();
-    return response;
+    return PutCustomerResponse.to(response);
   }
 
   public void deleteCustomer(Sep10Jwt sep10Jwt, String account, String memo, String memoType)