Pull config via `@ConfigProperty` in mirror-service

[nscuro]

Description

[!NOTE] ~This PR is based on #1223. Please review that first, I'll update this PR once it is merged. Should drastically reduce the change size. :)~

Replaces properties pulled from application.properties / environment variables to configure datasources in mirror-service, with properties from the CONFIGPROPERTY database table. This is achieved via the quarkus-config-dependencytrack extension introduced in #1223.

Addressed Issue

Relates to #929

Additional Details

• mirror-service now requires a database connection
• mirror-service now requires access to the secret key, in order to decrypt API secrets
• Config properties are not cached, due to the low frequency at which they'll be queried

Checklist

• [x] I have read and understand the contributing guidelines
• ~This PR fixes a defect, and I have provided tests to verify that the fix is effective~
• [x] This PR implements an enhancement, and I have provided tests to verify that it works as intended
• ~This PR introduces changes to the database model, and I have updated the migration changelog accordingly~
• ~This PR introduces new or alters existing behavior, and I have updated the documentation accordingly~

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
:white_check_mark: +2.64% (target: -1.00%)	∅ (target: 70.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (6aff04502596cef6dc469b939cb3ec5dc4c73fcf)	172	140	81.40%
Head commit (711bfb29e2954e056590e319501c54ae8b5945b8)	6715 (+6543)	5643 (+5503)	84.04% (+2.64%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#1236)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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