feat(dynamic-sampling): add endpoint to retrieve project span counts

[shellmayr]

• Expose the span counts in all projects of an org via a new endpoint at /{organization}/sampling/project-span-counts/
• API response format is the same as in the metrics/query API
• Allows all members of an org with org:read permissions or higher to access the project ids, project names, and span counts of all projects in the org, even if there is no open membership

Contributes to https://github.com/getsentry/projects/issues/353

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Additional details and impacted files

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  Branches    43907    43976      +69     
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+ Hits       249778   250340     +562     
- Misses      62585    62616      +31     
- Partials     6361     6374      +13     

[constantinius]

I think this is a potential issue. Queryset .all() does nothing but copy the queryset, which is basically an iterator and not really a sequence. typing.cast is essentially a no-op functionally, just there for typing. If you require an actual sequence I would use projects = list(Projects.objects.filter(...)).

[jan-auer]

Cast to Sequence should no longer be required - a list is a sequence. Also, list() will evaluate the queryset, I think you can omit the .all().

Optionally, I'd add a comment to clarify that we do not want team filters even with closed membership, so that in the future this is not unintentionally "fixed".

Suggested change

	projects = cast(
	Sequence[Project],
	list(
	Project.objects.filter(organization=organization, status=ObjectStatus.ACTIVE).all()
	),
	)
	projects = list(
	Project.objects.filter(organization=organization, status=ObjectStatus.ACTIVE)
	)

[jan-auer]

This endpoint returns the span count per root project, which distinguishes it from regular stats endpoints. Should we choose a URL that makes this clear? This might make the URL too long, so I'm not sure we should actually do this.

Options could be:

• project-root-counts (we can equally add other counts there if we need to)
• span-root-counts
• root-counts

[shellmayr]

Yeah that's a good point. None of them really feel intuitive to me, but I suppose project-root-counts is probably the best, as it even takes out the specificity of spans in case we ever adapt what type of data sampling acts on.

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ MetricsQueryExecutionError: An error occurred while executing the query /api/0/organizations/{organization_id_or_slug}/... View Issue

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