feat: Expose metrics about used TeamForCapella license usage

[MoritzWeber0]

A new gauge metric t4c_licenses was added to the /metrics endpoint, which contains the number of currently used licenses per TeamForCapella instance. The instance name is used as label for the metric.

Note: If you have multiple TeamForCapella server instances, which point to the same license server, this is not detected. Therefore, make sure to filter the t4c_licenses for one instance first.

Resolves #693.

[codecov]

Codecov Report

Attention: Patch coverage is 85.00000% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 73.11%. Comparing base (21d4c9a) to head (98fc67e).
Report is 2 commits behind head on main.

Files	Patch %	Lines
...capellacollab/settings/modelsources/t4c/metrics.py	84.21%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1387      +/-   ##
==========================================
+ Coverage   72.99%   73.11%   +0.11%     
==========================================
  Files         164      165       +1     
  Lines        5451     5490      +39     
  Branches      618      624       +6     
==========================================
+ Hits         3979     4014      +35     
- Misses       1334     1335       +1     
- Partials      138      141       +3     

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

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[dominik003]

LGTM! I was going to suggest using an (abstract) collector class, since the two collectors are very similar (and there is the possibility to outsource the retrieval of the instances), but apparently there is already such an abstract class in the Prometheus client, but starlett-prometheus uses a rather old version of it where it is not yet added.