Store app settings (with some defaults in a separate file)

[amstilp]

• Add an app_settings file that handles settings specific to this app
• Update the code to use app_settings

[codecov[bot]]

Codecov Report

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

Project coverage is 99.74%. Comparing base (38fd0b7) to head (c75908c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #492 +/- ## ========================================== - Coverage 99.74% 99.74% -0.01% ========================================== Files 128 130 +2 Lines 23741 23857 +116 ========================================== + Hits 23681 23795 +114 - Misses 60 62 +2 ```

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