Add public creator ETag header helper

[Chucks1093]

Summary

Add a helper for setting ETag headers on public creator endpoints.

Acceptance Criteria

• helper can compute or accept an ETag value
• endpoints can reuse the helper without changing business logic
• works alongside existing cache headers

Contributor coordination: https://t.me/accesslayerorg

[Belzabeem]

@Belzabeem has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I would love to work on this issue

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[khanavi272-spec]

@khanavi272-spec has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @khanavi272-spec to this issue.

[drips-wave]

Congratulations, @Belzabeem! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @Belzabeem: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @Belzabeem as part of the Stellar Wave Program's 4th Wave 🥳

Moderator's reason: [Auto-assessed] The PR has been open for over 72 hours with no maintainer objections. The implementation of the ETag helper utility directly addresses the requirements of Issue #104 by providing functions to both generate and attach ETag headers to responses.

😎 @Belzabeem: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

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ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.