Tune JPA Eager/Lazy loading for performance

as part of the overall FINERACT-867, tuning JPA Eager/Lazy loading for performance is always fun.

FINERACT-902 is worth reading re. this topic. The goal of this issue would be to:

1. measure numbers of SQL queries per API call
2. measure the time of each such query, on "full" (non-demo) real database
3. see if throwing in a few more fetch=FetchType.LAZY annotation at the right place can help
4. use more fine grained per operation Fetch Plans instead annotations, based on measues