Enforce boolean defaults on Application Settings

What does this MR do?

Enforces defaults and disallows nulls on application_settings boolean columns.

Why was this MR needed?

New application settings have two "defaults":

• New install: When a record does not exist in application_settings, we use ApplicationSetting.defaults

• On upgrade: When a record exists, the value defaults to the column default

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #2750 (closed)

changed the description

added 248 commits

• 8cc60b0b...27df74ad - 246 commits from branch master
• cffa081f - Add SaferBooleanColumn cop
• 50d147fa - Exclude existing offenses

Compare with previous version

assigned to @DouweM

assigned to @mkozono

changed milestone to %10.0

resolved all discussions

approved this merge request

enabled an automatic merge when the pipeline for 50d147fa succeeds

@mkozono Build is failing; you may want to rebase.

added 1350 commits

• 50d147fa...12cdc461 - 1347 commits from branch master
• 9beef184 - Add SaferBooleanColumn cop
• c715936e - Exclude existing offenses
• 64a3c993 - WIP autocorrect?

Compare with previous version

marked as a Work In Progress from 64a3c9936fe48f6047b3b01e3f9cc6192f142de8

unmarked as a Work In Progress

approved this merge request

enabled an automatic merge when the pipeline for c715936e succeeds

merged

mentioned in commit 62216af8