feat(attributes): Add sentry.metric.source

[klochek]

Description

This is an attribute that can be used to attribute the source of a metric; for example, Relay can use it to indicate that a metric originated from an ingested span.

PR Checklist

• [*] I have run yarn test and verified that the tests pass.
• [*] I have run yarn generate to generate and format code and docs.
• [*] The attribute is in a namespace (e.g. nextjs.function_id, not function_id)
• [*] I have used the correct value for apply_scrubbing (i.e. manual or auto. Use never only for values that should never be scrubbed such as IDs)

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

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New Features ✨

Attributes

• Add sentry.metric.source by klochek in #476

• Add faas.id (deprecated) in favor of cloud.resource_id by andreiborza in #475
• Add faas.execution (deprecated) in favor of faas.invocation_id by andreiborza in #473
• Add messaging attributes by s1gr1d in #469
• Add url.same_origin (deprecated) and http.request.same_origin (replacement) attributes by Lms24 in #456
• Add db.response.status_code by s1gr1d in #462

Other

• (ai) Add granular cost attributes for cache and reasoning by vgrozdanic in #461

Internal Changes 🔧

• (ci) Stop inheriting secrets for changelog-preview by tobias-wilfert in #463

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[Lms24]

Generally no objections just a thought: Have we considered reusing sentry.origin?

The only thing that speaks a bit against sentry.metric.source is that there's sentry.span.source and it has a different meaning. Though we'll likely deprecate sentry.span.source anyway, so it's not too big a deal.

[klochek]

Generally no objections just a thought: Have we considered reusing sentry.origin?

The only thing that speaks a bit against sentry.metric.source is that there's sentry.span.source and it has a different meaning. Though we'll likely deprecate sentry.span.source anyway, so it's not too big a deal.

For our (Relay's) purposes, we're passing through sentry.origin since it contains the originating web vital name, like "auto.http.browser.inp". Perhaps we could repurpose it on our end for the metric provenance, but I feel like it'd be safer not to.

[logaretm]

While I don't exactly remember why we didn't consider re-using the origin initially, I think preserving it from the span origin could be desirable here, so a new attribute is needed to avoid having web vital spans with diverging origins. Does that make sense?

[Lms24]

Makes sense, thx for explaining!