feat: Made all log statements adhering to GELF format

[dadrus]

closes #151

[codecov]

Codecov Report

Merging #259 (8696763) into main (ac7bebb) will decrease coverage by 0.05%.
The diff coverage is 81.25%.

@@            Coverage Diff             @@
##             main     #259      +/-   ##
==========================================
- Coverage   85.98%   85.92%   -0.06%     
==========================================
  Files         156      156              
  Lines        6522     6531       +9     
==========================================
+ Hits         5608     5612       +4     
- Misses        782      787       +5     
  Partials      132      132              

Impacted Files	Coverage Δ
internal/handler/decision/module.go	40.35% <0.00%> (ø)
internal/handler/management/module.go	40.35% <0.00%> (ø)
internal/handler/prometheus/module.go	0.00% <0.00%> (ø)
internal/handler/proxy/module.go	41.37% <0.00%> (ø)
internal/pipeline/hydrators/generic_hydrator.go	81.27% <60.00%> (+0.07%)	⬆️
internal/rules/provider/filesystem/file_system.go	81.03% <78.57%> (-0.26%)	⬇️
internal/keystore/module.go	79.41% <100.00%> (+2.74%)	⬆️
internal/logging/configuration.go	100.00% <100.00%> (ø)
...ernal/pipeline/authenticators/jwt_authenticator.go	91.55% <100.00%> (ø)
internal/pipeline/authorizers/remote_authorizer.go	80.66% <100.00%> (+0.07%)	⬆️
... and 8 more

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