### Steps to reproduce

1. Define ideally multiple custom fields of various types on 'Spent time'/time entries

2. Have a list of time entries

3. Fetch the time entries calling /api/v3/time\_entries

4. Look at the SQL statements issued


### What is the buggy behavior?

* n+1 queries for

* Begin of the insertion~~TheEnd of the insertion Begin of the deletion TheEnd of the deletion custom Begin of the insertionvalues~~ (fixed in the first PR)End of the insertion Begin of the deletion valuesEnd of the deletion

* Begin of the insertion~~TheEnd of the insertion Begin of the deletion TheEnd of the deletion custom Begin of the insertionfields~~ (fixed in the first PR)End of the insertion Begin of the deletion fieldsEnd of the deletion

* The non scalar values (e.g. users)


### What is the expected behavior?

No n+1 queries -> improved performance