feat(webapi): Add ExternalReference to dialog search result (#1384)

<!--- Provide a general summary of your changes in the Title above -->

## Description

<!--- Describe your changes in detail -->

## Related Issue(s)

- #1376 

## Verification

- [ ] **Your** code builds clean without any errors or warnings
- [ ] Manual testing done (required)
- [ ] Relevant automated test added (if you find this hard, leave it and
we'll help out)

## Documentation

- [ ] Documentation is updated (either in `docs`-directory, Altinnpedia
or a separate linked PR in
[altinn-studio-docs.](https://github.com/Altinn/altinn-studio-docs), if
applicable)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Introduced an `externalReference` property in the dialog schema,
enhancing metadata for better integration with external systems.
- Added an `ExternalReference` property in the `DialogDtoBase` class for
service-specific references to external systems.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

docs/schema/V1/swagger.verified.json

@@ -1337,6 +1337,11 @@
             "nullable": true,
             "type": "string"
           },
+          "externalReference": {
+            "description": "Arbitrary string with a service-specific reference to an external system or service.\n            \nRefer to the service-specific documentation provided by the service owner for details (if in use).",
+            "nullable": true,
+            "type": "string"
+          },
           "guiAttachmentCount": {
             "description": "The number of attachments in the dialog made available for browser-based frontends.",
             "format": "int32",
@@ -4352,6 +4357,11 @@
             "nullable": true,
             "type": "string"
           },
+          "externalReference": {
+            "description": "Arbitrary string with a service-specific reference to an external system or service.\n            \nRefer to the service-specific documentation provided by the service owner for details (if in use).",
+            "nullable": true,
+            "type": "string"
+          },
           "guiAttachmentCount": {
             "description": "The number of attachments in the dialog made available for browser-based frontends.",
             "format": "int32",
@@ -7445,4 +7455,4 @@
       "url": "https://altinn-dev-api.azure-api.net/dialogporten"
     }
   ]
-}
+}

src/Digdir.Domain.Dialogporten.Application/Features/V1/EndUser/Dialogs/Queries/Search/DialogDtoBase.cs

@@ -71,6 +71,13 @@ public class DialogDtoBase
     /// </summary>
     public string? ExtendedStatus { get; set; }
 
+    /// <summary>
+    /// Arbitrary string with a service-specific reference to an external system or service.
+    ///
+    /// Refer to the service-specific documentation provided by the service owner for details (if in use).
+    /// </summary>
+    public string? ExternalReference { get; set; }
+
     /// <summary>
     /// The date and time when the dialog was created.
     /// </summary>

src/Digdir.Domain.Dialogporten.Application/Features/V1/ServiceOwner/Dialogs/Queries/Search/DialogDtoBase.cs

@@ -77,6 +77,13 @@ public class DialogDtoBase
     /// </summary>
     public string? ExtendedStatus { get; set; }
 
+    /// <summary>
+    /// Arbitrary string with a service-specific reference to an external system or service.
+    ///
+    /// Refer to the service-specific documentation provided by the service owner for details (if in use).
+    /// </summary>
+    public string? ExternalReference { get; set; }
+
     /// <summary>
     /// The date and time when the dialog was created.
     /// </summary>