feat(azure_blob sink): support blob index tags and metadata

[Danielku15]

Summary

Adds blob tags and metadata support to the azure_blob sink. This updates request building and Azure common config handling so tags/metadata are forwarded correctly, and adds unit + Azurite-backed integration coverage for the new behavior.

Vector configuration

Example config used during testing:

sinks:
  azure_blob:
    type: azure_blob
    inputs:
      - my_source
    connection_string: ${AZURE_STORAGE_CONNECTION_STRING}
    container_name: logs
    blob_prefix: vector/
    encoding:
      codec: text
    tags:
      env: prod
      team: platform
    metadata:
      source: vector
      region: us-east-1

How did you test this PR?

Ran:

• cargo fmt --all --check
• cargo clippy --no-default-features --features sinks-azure_blob --tests -- -D warnings
• cargo test --no-default-features --features sinks-azure_blob azure_blob_build_request_with_blob_ -- --nocapture
• cargo test --no-default-features --features sinks-azure_blob,azure-blob-integration-tests sinks::azure_blob::integration_tests:: -- --nocapture
• cargo vdev check generated-docs
• cargo vdev check markdown
• ./scripts/check_changelog_fragments.sh

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Closes: #22316

Notes

No notes from my side.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[Danielku15]

I have read the CLA Document and I hereby sign the CLA

[Danielku15]

Any of the maintainers around who can give feedback this feature contribution? I'd like to also implement the AppendBlob support soon-ish and this makes most sense with this feature also in place.

The two features would be quite crucial for us to use vector.dev in product, without them we need to look for some alternative solutions. No intention to be pushy, just trying to understand the general release cycle and policies on external contributions 😉

[Danielku15]

@codex review

[chatgpt-codex-connector]

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[rtrieu]

hi @Danielku15 left you some editorial suggestions for your consideration.

[Danielku15]

@rtrieu Thanks for the feedback. I've applied all changes.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 89d143a6f8

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[jlaundry]

Hi @Danielku15, I'm not a maintainer, but have done a bunch of Azure sink stuff recently.

This looks good! Two comments:

1. Given the 10 tag limit, as well as a 128 character key limit and 256 character value limit, should these be checked during the config build, so that there's an clear error for the user to fix?
2. FYI, it's been on my list to move the Blob-specific code out of azure_common, and I've opened chore(azure sinks): refactor Blob code out of azure_common #25689 this morning. I'm a bit late with this, and I'm happy to rebase my PR if this merges first.