fix: identity CIDs use contentTypeParser

[SgtPooki]

Title

fix: identity CIDs use contentTypeParser

Description

latest update of @helia/verified-fetch caused failing tests in service-worker-gateway: https://github.com/ipfs-shipyard/service-worker-gateway/pull/187

Fixes https://github.com/ipfs/helia-verified-fetch/issues/48

Notes & open questions

This change normalizes how we handle setting content-type for raw CIDs and identity CIDs and was required to ensure that the content-type is set correctly for identity CIDs.

Change checklist

• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation if necessary (this includes comments as well)
• [x] I have added tests that prove my fix is effective or that my feature works

[SgtPooki]

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[github-actions[bot]]

:tada: This PR is included in version 1.3.9 :tada:

The release is available on npm package (@latest dist-tag)

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[github-actions[bot]]

:tada: This PR is included in version 1.16.0 :tada:

The release is available on npm package (@latest dist-tag)

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[github-actions[bot]]

:tada: This PR is included in version 1.0.0 :tada:

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