[Instrumentation.Hangfire] Add metrics support

[gorbach]

Fixes #2075

Changes

Adds OpenTelemetry metrics support to Hangfire instrumentation following workflow semantic conventions.

Implemented metrics:

• workflow.execution.count - Counter for task executions
• workflow.execution.duration - Histogram for execution duration
• workflow.execution.status - UpDownCounter for state transitions
• workflow.execution.errors - Counter for execution errors
• hangfire.queue.latency - Optional histogram for queue wait time

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated
• CHANGELOG.md updated
• Changes in public API reviewed

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Kielek / name: Piotr Kiełkowicz (4b95bb7, aa2d422)

[thompson-tomo]

Looks to be a good step forward and I have suggested a couple of changes here as well as to the sem conv based on the learnings.

[Kielek]

@gorbach, please check this comment #2075 (comment)

The second point is technical requirements to separate metrics/traces signal. It will be great to rename classes in the separate PR and then merge it/rebase here.

[thompson-tomo]

Looking good. Only 1 design question #3258 (comment) which when resolved would mean I approve.

[thompson-tomo]

Have left a bunch of nits for things which could be improved/simplified.

[gorbach]

I beleive I've fixed all linter warnings, compilation errors (in release) and ran dotnet format for tests and code.

[codecov]

Codecov Report

❌ Patch coverage is 85.76159% with 43 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.21%. Comparing base (55aa86e) to head (aa2d422).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...entation.Hangfire/Implementation/TypeExtensions.cs	33.33%	16 Missing ⚠️
...gfire/Implementation/HangfireMetricsStateFilter.cs	77.96%	13 Missing ⚠️
...tion.Hangfire/Implementation/HangfireTagBuilder.cs	89.47%	8 Missing ⚠️
...entation/HangfirePendingDurationFilterAttribute.cs	84.61%	4 Missing ⚠️
...mplementation/HangfireMetricsJobFilterAttribute.cs	92.85%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3258      +/-   ##
==========================================
+ Coverage   70.80%   71.21%   +0.40%     
==========================================
  Files         440      442       +2     
  Lines       17265    17516     +251     
==========================================
+ Hits        12225    12474     +249     
- Misses       5040     5042       +2     

Flag	Coverage Δ
unittests-Instrumentation.Cassandra	?
unittests-Instrumentation.Hangfire	86.05% <85.76%> (+1.43%)	⬆️

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

Files with missing lines	Coverage Δ
....Hangfire/HangfireMetricsInstrumentationOptions.cs	100.00% <100.00%> (ø)
...ntation.Hangfire/Implementation/HangfireMetrics.cs	100.00% <100.00%> (ø)
...lementation/HangfireMetricsErrorFilterAttribute.cs	100.00% <100.00%> (ø)
...e/Implementation/HangfireMetricsInstrumentation.cs	100.00% <100.00%> (ø)
...ion.Hangfire/Implementation/HangfireStateMapper.cs	100.00% <100.00%> (ø)
...tation.Hangfire/Implementation/JobNameFormatter.cs	100.00% <100.00%> (ø)
...ntation.Hangfire/MeterProviderBuilderExtensions.cs	100.00% <100.00%> (ø)
...mplementation/HangfireMetricsJobFilterAttribute.cs	92.85% <92.85%> (ø)
...entation/HangfirePendingDurationFilterAttribute.cs	84.61% <84.61%> (ø)
...tion.Hangfire/Implementation/HangfireTagBuilder.cs	89.47% <89.47%> (ø)
... and 2 more

... and 11 files with indirect coverage changes

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[thompson-tomo]

Note these changes would be necessary once #3545 is merged so might be better to merge them now. Could a maintainer commit my suggestions?

[Kielek]

LGTMRS

[problesal-sacyr]

Hi, when's this hitting NuGet? Thanks!

[Kielek]

Someone needs to create https://github.com/open-telemetry/opentelemetry-dotnet-contrib/issues/new?template=release_request.yml. Probably 1.14.0-beta.2 version.