Feature export Harbor statistics as Prometheus metric

[tpoxa]

This PR exposes the Harbor statistics as Prometheus metric.

The data exposed as metrics are 1:1 taken from thestatistics API, including the name.

New Metrics

• harbor_statistics_private_project_amount
• harbor_statistics_private_repo_amount
• harbor_statistics_public_project_amount
• harbor_statistics_public_repo_amount
• harbor_statistics_total_project_amount
• harbor_statistics_total_repo_amount
• harbor_statistics_total_storage_consumption

Please indicate you've done the following:

• Well-Written Title and Summary of the PR
• Label the PR as needed. release-note/enhancement
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[codecov]

Codecov Report

Attention: Patch coverage is 58.88889% with 37 lines in your changes missing coverage. Please review.

Project coverage is 66.27%. Comparing base (c8c11b4) to head (7ea6628).
Report is 265 commits behind head on main.

Files	Patch %	Lines
src/pkg/exporter/statistics_collector.go	60.91%	27 Missing and 7 partials ⚠️
src/pkg/exporter/exporter.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #18679       +/-   ##
===========================================
+ Coverage   45.36%   66.27%   +20.90%     
===========================================
  Files         244     1047      +803     
  Lines       13333   114251   +100918     
  Branches     2719     2845      +126     
===========================================
+ Hits         6049    75722    +69673     
- Misses       6983    34400    +27417     
- Partials      301     4129     +3828     

Flag	Coverage Δ
unittests	66.27% <58.88%> (+20.90%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/pkg/exporter/exporter.go	6.66% <0.00%> (ø)
src/pkg/exporter/statistics_collector.go	60.91% <60.91%> (ø)

... and 1285 files with indirect coverage changes

[Vad1mo]

Works great, thank you

[github-actions]

This PR is being marked stale due to a period of inactivty. If this PR is still relevant, please comment or remove the stale label. Otherwise, this PR will close in 30 days.

[github-actions]

This PR was closed because it has been stalled for 30 days with no activity. If this PR is still relevant, please re-open a new PR against main.

[wy65701436]

@Vad1mo since we've reached the FC of v2.10 this week, I just put it into the v2.11 candidate.

[Vad1mo]

@wy65701436 any chance we can get this merged into 2.11?

[Vad1mo]

@goharbor/all-maintainers, can we get this merged? we have it now running since 1 year in prod across multiple instances and I don't see a reason not merging it.

[chlins]

@tpoxa Hi, I have several questions about this PR, as follows:

1. The description says that the metric name taken from response from statistics API, but in the API response it is private_project_count not private_project_amount, and IMH the name should follow the name style of previous metrics.
2. I think some metrics are duplicated with previous metrics, FYI: https://goharbor.io/docs/main/administration/metrics/.
3. The docs should be updated as well if we add some new metrics to harbor.