We currently have the following types of metadata:

Metadata
  user_id: UUID
  account_id: UUID
  correlation_id: UUID
  causation_id: UUID
  migrated: bool
  metadata_type: "attributed"

UnattributedMetadata | SystemMetadata
  account_id: UUID
  correlation_id: UUID
  causation_id: UUID
  migrated: bool
  metadata_type: "unattributed" | "system"

I see two categories of fields here, some domain specific ones (user_id, account_id, migrated) and event sourcing ones (correlation_id, causation_id). There is also a type field that we use to choose the right metadata class when we load it.

The domain specific fields don't belong in the event framework, so we need some way to configure what class(es) that can be used by the framework.

We also need to think of a way to serialize/deserialize the different types of metadata.

I think I would also like to move correlation_id and causation_id to the Event class and probably store them directly on the events table. That way we would have a clearer separation between the domain/app specific metadata and the more general fields that we may want to set/read from the framework.