postgres comments

[jstucke]

• added table and column comments for documentation purposes and for displaying in the GraphiQL docs

ToDo:

• [x] generate alembic migration script

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.87%. Comparing base (50a0bf4) to head (4e63303). Report is 690 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1231 +/- ## ========================================== - Coverage 95.33% 91.87% -3.46% ========================================== Files 347 376 +29 Lines 20034 21075 +1041 ========================================== + Hits 19099 19363 +264 - Misses 935 1712 +777 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.