Add db entry metrics

[zealsham]

this pr addresses the db entries part of #941 , it adds db entries metrics seperated by version (v1/v2). For now it's just simple incremental counter seperated by v1/v2.

Pull Request Checklist

Please confirm the following before requesting review:

• I have disclosed my use of
  AI
  in the body of this PR.
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Pull Request Test Coverage Report for Build 23021001559

Details

• 63 of 69 (91.3%) changed or added relevant lines in 3 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.05%) to 83.845%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
payjoin-mailroom/src/lib.rs	8	14	57.14%

Files with Coverage Reduction	New Missed Lines	%
payjoin-mailroom/src/directory.rs	2	85.94%

Totals
Change from base Build 23006553249:	0.05%
Covered Lines:	10707
Relevant Lines:	12770

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💛 - Coveralls