Improve exception handling and refactor unused methods in changes

src/SIL.Harmony/Changes/CreateChange.cs

@@ -1,9 +1,12 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+
 namespace SIL.Harmony.Changes;
 
 public abstract class CreateChange<T>(Guid entityId) : Change<T>(entityId) where T : class
 {
     public override ValueTask ApplyChange(T entity, IChangeContext context)
     {
-        throw new NotSupportedException($"type {GetType().Name} does not support ApplyChange, because it inherits from {nameof(CreateChange<T>)}, this means it must be called with a new Guid and not one from an existing entity");
+        //won't be called because it's skipped by the base class for CreateChange
+        return default;
     }
 }

src/SIL.Harmony/Changes/EditChange.cs

@@ -1,3 +1,5 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+
 namespace SIL.Harmony.Changes;
 
 public abstract class EditChange<T>(Guid entityId) : Change<T>(entityId)
@@ -6,6 +8,6 @@ public abstract class EditChange<T>(Guid entityId) : Change<T>(entityId)
     public override ValueTask<T> NewEntity(Commit commit, IChangeContext context)
     {
         throw new NotSupportedException(
-            $"type {GetType().Name} does not support NewEntity, because it inherits from {nameof(EditChange<T>)}, this means it must be called with a from an existing entity, not a newly generated one");
+            $"type {GetType().ShortDisplayName()} does not support NewEntity, because it inherits from {nameof(EditChange<T>)}, this means it must be called with an existing entity, not a newly generated one. CommitId: {commit.Id}, EntityId: {EntityId}");
     }
 }