I have been trying to create a migrator for the Our Umbraco Migrations package but it doesn't even run.

The basic structure of the class looks like this:

[DataTypeMigrator("Imulus.UrlPicker")]
public class ImulusUrlPickerMigrator : JsonContentMigrator<JArray>
{
      public override string GetNewPropertyEditorAlias(IDataTypeDefinition dataType, IDictionary<string, PreValue> oldPreValues) => "Umbraco.MultiUrlPicker";

      protected override IEnumerable<IJsonPropertyTransform<JArray>> GetJsonPropertyTransforms(IDataTypeDefinition dataType, IDictionary<string, PreValue> oldPreValues, bool retainInvalidData)
      {
        yield return new JsonPropertyTransform<JArray>
        {
            Migration = new ImulusUrlPickerMigration(),
            PropertyValuesAndSetters = GetValuesAndSetters
        };
      }
}

Not all code is here, it also includes some code copied from the Archetype Migrator that comes with the package. The main thing is that the migrator doesn't run at all :(

I thought this migrator should be picked up automatically by the DefaultIdToUdiMigration but apparently it's not.

Other migrators run properly so the actual migration is running, it's just this migrator doesn't run.

Any ideas about what I'm missing?