adding

LCU.API.Internal.Document/OwnerNumberMigration/Logging/AttributeMigrationLoggingObserver.cs

@@ -0,0 +1,33 @@
+using LCU.API.Internal.DocumentLib.Containers;
+using Microsoft.Extensions.Logging;
+
+namespace OwnerNumberMigration.Logging;
+
+public delegate IObserver<DocumentInformation> AttributeMigrationLoggingObserverFactory(string attributeName);
+
+public class AttributeMigrationLoggingObserver : IObserver<DocumentInformation>
+{
+    private readonly ILogger _logger;
+    private readonly string _attributeName;
+
+    public AttributeMigrationLoggingObserver(ILogger logger, string attributeName)
+    {
+        _logger = logger;
+        _attributeName = attributeName;
+    }
+
+    public void OnCompleted()
+    {
+        _logger.LogInformation("completed one migration for {attribute}", _attributeName);
+    }
+
+    public void OnError(Exception error)
+    {
+        _logger.LogError("migration error {error} in migration for {attribute}", error, _attributeName);
+    }
+
+    public void OnNext(DocumentInformation value)
+    {
+        _logger.LogInformation("starting one migration for {attribute} on {documentId}", _attributeName, value.DocumentId);
+    }
+}