Update domain objects to contain minimum set

[ykamo001]

We are querying for the entire domain object in NotificationMessage repository. Instead of doing this, try to only query and retain the minimum set of data needed (aggregate root) for the domain object. Look for this ticket in the comments to find the areas that need updating.

[getsantry]

Routing to @getsentry/product-owners-issues for triage ⏲️