multi: register with different assets, add BTC

This permits payment of registration fee in different assets, and adds BTC.

* dex/msgjson: update config and register

Asset ID in Register and RegisterResult.

RegFees map in ConfigResult.  New FeeAsset type.

* server/db: external key derivation, add fee_asset

Add FeeAsset uint32 to the db.Account type and accounts table.

HD key derivation and address generation is no longer the role of the
database driver.

Add the db.KeyIndexer interface, which retrieves and records an
integer index for a []byte, a serialized pubkey corresponding to
a master pubkey's child and it's index.
DEXArchivist is now required to be a KeyIndexer.

CreateAccount now requires asset ID and reg address provided as inputs
rather than it generating and returning a reg address.
AccountRegAddr now also returns asset ID with the address.

* server/asset: Addresser and HDKeyIndexer

Add fee address generators to DCR and BTC.

Implement FeeCoin (fee checker) in BTC.

* server/auth: use multi-asset fee addressers and checkers

* server/cmd/dcrdex: per-asset fee config

* server/dex: per-asset fee stitching

FeeCoiner and AddresserFactor provide the helpers for the auth manager.

Update the config response with the RegFees field.

Start archivist before asset backends because the fee Addressers require
it for key index storage and retrieval.

* client/{core.db}: multi-asset fees with FeeAssetID

client/db:

This adds db.AccountInfo.FeeAssetID uint32, and updates the DB encoding.

v2 db.AccountInfo encoding is updated, and fields reordered.
When earlier (v0/v1) blobs are loaded, FeeAssetID is loaded as 42.

client/core:

Add asset ID to RegisterForm.

Add Exchange.RegFees map[string]*FeeAsset field, and a PendingFeeState
struct field that describes the asset and confs of the pending fee,
removing the RegConfirms ('confs') field. Also remove the
ConfsRequired ('confsrequired') and FeePending ('feePending') fields.

Add feeAssetID uint32 to dexAccount.

In Core, use the Exchange.RegFees map, and deal with older servers
providing the old config response.

Change (*Core).GetFee to (*Core).GetRegFees, which is unused.

Update FeePaymentNote with Asset *uint32.

* client/rpcserver and dexcctl

Kill getfee. Implement getdexconfig instead.

* client/webserver: specify DCR/42, but update handlers

Update apiRegister and registrationForm with asset ID.

Kill apiGetFee.

Modify js for pendingFee in FeePaymentNote, and removed confs and
confsrequired from Exchange struct (this.market.dex).

Frontend still defaults to DCR/42, no selection yet.

client/cmd/dexcctl/dexcctl_test.go

@@ -108,22 +108,22 @@ func TestReadTextFile(t *testing.T) {
 		wantErr                           bool
 	}{{
 		name:        "ok with cert",
-		cmd:         "getfee",
+		cmd:         "getdexconfig",
 		args:        []string{"1.2.3.4:3000", "./cert"},
 		txtFilePath: "./cert",
 		txtToSave:   certTxt,
 		want:        []string{"1.2.3.4:3000", certTxt},
 	}, {
 		name: "ok no cert",
-		cmd:  "getfee",
+		cmd:  "getdexconfig",
 		args: []string{"1.2.3.4:3000"},
 		want: []string{"1.2.3.4:3000"},
 	}, {
 		name: "not a readCerts command",
 		cmd:  "not a real command",
 	}, {
 		name:    "no file at path",
-		cmd:     "getfee",
+		cmd:     "getdexconfig",
 		args:    []string{"1.2.3.4:3000", "./cert"},
 		wantErr: true,
 	}, {

client/cmd/dexcctl/main.go

@@ -67,9 +67,9 @@ var promptPasswords = map[string][]string{
 // the text content of a file, where the file path _may_ be found in the route's
 // cmd args at the specified index.
 var optionalTextFiles = map[string]int{
-	"getfee":    1,
-	"register":  2,
-	"newwallet": 1,
+	"getdexconfig": 1,
+	"register":     3,
+	"newwallet":    1,
 }
 
 // promptPWs prompts for passwords on stdin and returns an error if prompting

client/cmd/dexcctl/simnet-setup.sh

@@ -41,7 +41,7 @@ if [ $ETH_ON -eq 0 ]; then
 fi
 
 echo registering with DEX
-./dexcctl -p abc --simnet register 127.0.0.1:17273 100000000 ~/dextest/dcrdex/rpc.cert
+./dexcctl -p abc --simnet register 127.0.0.1:17273 100000000 42 ~/dextest/dcrdex/rpc.cert
 
 echo mining fee confirmation blocks
 tmux send-keys -t dcr-harness:0 "./mine-alpha 1" C-m

client/core/bookie.go

@@ -662,6 +662,33 @@ func (dc *dexConnection) refreshServerConfig() error {
 			}
 		}
 	}
+
+	// Patch ConfigResponse.RegFees if no entry for DCR is there, meaning it is
+	// likely an older server using cfg.Fee and cfg.RegFeeConfirms.
+	if dcrAsset := cfg.RegFees["dcr"]; dcrAsset == nil {
+		dc.log.Warnf("Legacy server %v does not provide a regFees map.", dc.acct.host)
+		if cfg.RegFees == nil {
+			cfg.RegFees = make(map[string]*msgjson.FeeAsset)
+		}
+		if cfg.Fee > 0 {
+			cfg.RegFees["dcr"] = &msgjson.FeeAsset{ // v0 is only DCR
+				ID:    42,
+				Confs: uint32(cfg.RegFeeConfirms),
+				Amt:   cfg.Fee,
+			}
+		} else {
+			dc.log.Warnf("Server %v does not support DCR for registration", dc.acct.host)
+		}
+	} else {
+		if cfg.Fee > 0 && dcrAsset.Amt != cfg.Fee {
+			dc.log.Warnf("Inconsistent DCR fee amount: %d != %d", dcrAsset.Amt, cfg.Fee)
+		}
+		if dcrAsset.Confs != uint32(cfg.RegFeeConfirms) {
+			dc.log.Warnf("Inconsistent DCR fee confirmation requirement: %d != %d",
+				dcrAsset.Confs, cfg.RegFeeConfirms)
+		}
+	}
+
 	// Update the dex connection with the new config details, including
 	// StartEpoch and FinalEpoch, and rebuild the market data maps.
 	dc.cfgMtx.Lock()