Currently it's redundant and not easy to read.
```
{"message":"JSON object requested, multiple (or no) rows returned",
"details":"The result contains 2 rows"}
```
Now:
```
{"message":"Cannot coerce the result to a single JSON object",
"details":"The result contains an array of 0 objects"}
``
Also correct docs which had a wrong error code.
* Don't apply `tx=commit` if the transaction doesn't commit
* Apply `count=exact`
* Also simplifies the Preference-Applied logic, removing the need for
some functions.
- Revert patch #2311
- Keep the refactor done to qsFiltersRoot
- Keep the refactor done to the items tables
- Add tests that now work with pg-safeupdate as a result
