feat(subscription): add operation_name label to apollo.router.opened.subscriptions counter (backport #7606)

[bnjjj]

This PR adds a new label on apollo.router.opened.subscriptions metric to know exactly which subscription is still opened.

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Checklist

Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• Changes are compatible¹
• Documentation² completed
• Performance impact assessed and acceptable
• Metrics and logs are added³ and documented
• Tests added and passing⁴
  • Unit Tests
  • Integration Tests
  • Manual Tests

Exceptions

Note any exceptions here

Notes

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This is an automatic backport of pull request #7606 done by [Mergify](https://mergify.com).

Footnotes

1. It may be appropriate to bring upcoming changes to the attention of other (impacted) groups. Please endeavour to do this before seeking PR approval. The mechanism for doing this will vary considerably, so use your judgement as to how and when to do this. ↩

2. Configuration is an important part of many changes. Where applicable please try to document configuration examples. ↩

3. A lot of (if not most) features benefit from built-in observability and debug-level logs. Please read this guidance on metrics best-practices. ↩

4. Tick whichever testing boxes are applicable. If you are adding Manual Tests, please document the manual testing (extensively) in the Exceptions. ↩

[mergify]

Cherry-pick of e7b7e40 has failed:

On branch mergify/bp/1.x/pr-7606
Your branch is up to date with 'origin/1.x'.

You are currently cherry-picking commit e7b7e401.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   .changesets/fix_bnjjj_add_operation_name_subscription_metric.md
	modified:   apollo-router/src/notification.rs
	modified:   apollo-router/src/plugins/subscription.rs
	modified:   apollo-router/src/services/subgraph_service.rs
	modified:   apollo-router/src/services/supergraph/tests.rs
	modified:   apollo-router/tests/integration/mod.rs
	renamed:    apollo-router/tests/integration/subscription.rs -> apollo-router/tests/integration/subscription_load_test.rs
	modified:   dev-docs/metrics.md

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   apollo-router/src/metrics/mod.rs
	both modified:   docs/source/routing/observability/telemetry/instrumentation/standard-instruments.mdx

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[apollo-librarian]

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File Changes

0 new, 5 changed, 0 removed

* (developer-tools)/apollo-mcp-server/(latest)/command-reference.mdx
* (developer-tools)/rover/commands/dev.mdx
* graphos/routing/(latest)/observability/telemetry/instrumentation/standard-instruments.mdx
* graphos/routing/v1/observability/telemetry/instrumentation/standard-instruments.mdx
* graphos/schema-design/federated-schemas/reference/moving-to-federation-2.mdx

Build ID: 7b1f90c6fc01df10a68d7495

URL: https://www.apollographql.com/docs/deploy-preview/7b1f90c6fc01df10a68d7495

[apollo-librarian]

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Build ID: 7b1f90c6fc01df10a68d7495