Aa-fleetpings

Added

- Tests
- `allianceauth-app-utils` to replace built-in functions

Changed

- Minimum Python version set to 3.7
- Minimum AA version set to 2.8.8

Added

- Python 3.9 and Django 3.2 compatibility

Fixed

- Using Django application registry instead of directly accessing `INSTALLED_APPS` (49)

Fixed

- Interference with Discord service migrations in case the Discord service is
activated _after_ this app is installed.

Added

- Permission checks for "Create SRP Link" checkbox, so only FCs who have the
permission to actually add SRP links can use this feature ([46])

Fixed

- Creating multiple SRP links with the same SRP code.

Fixed

- An issue where additionally configured ping targets wouldn't show up in the
dropdown ([44])

Changed

- Set input field for formup time to `autocomplete="off"` so you don't have to fiddle
around to use the datetime picker anymore