reactivate clan-list/view with the new m2m client

[fcaps]

closes #459
related #445

as a part of the refactoring i had to remove the old code (it was not maintainable anymore) and updated it to work with the new m2m client, services and repository pattern.

The single view: (the leave clan is not implemented and will be done in another ticket)

List view:

The filter is instant (no backend call) and is bound to filter tag, name or leader.

Caching for clans/clan is 60min and should be purged if we add the clan-management again, so we purge only if needed.
There is also the possibility to "warmup" the clan cache, but this could be handled in another ticket.

[codecov]

Codecov Report

Attention: 35 lines in your changes are missing coverage. Please review.

Comparison is base (d231e86) 46.26% compared to head (28e374e) 48.12%.

Files	Patch %	Lines
src/backend/services/DataRepository.js	62.29%	11 Missing and 12 partials ⚠️
src/backend/routes/views/dataRouter.js	33.33%	6 Missing ⚠️
src/backend/routes/views/clanRouter.js	50.00%	1 Missing and 2 partials ⚠️
src/backend/services/ClanService.js	86.95%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #519      +/-   ##
===========================================
+ Coverage    46.26%   48.12%   +1.86%     
===========================================
  Files           56       58       +2     
  Lines         1204     1309     +105     
  Branches       131      154      +23     
===========================================
+ Hits           557      630      +73     
- Misses         633      649      +16     
- Partials        14       30      +16     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[fcaps]

@beckpaul you wanna try reviewing this?

[fcaps]

i know i should cover the error-cases a bit better, but somehow my joy writing tests has limits...