Implement API changelog generation from OpenAPI spec diffs

[Smartdevs17]

Context

API changes lack documentation. Developers manually write changelog entries that are frequently forgotten, inaccurate, or omitted.

Current Limitation/Problem

Changelog is a manually maintained markdown file that falls out of sync with actual API changes. Breaking changes are not always documented.

Expected Outcome

Automated changelog generation: compare OpenAPI specs between releases, categorize changes (breaking, additive, deprecation), and publish changelog to developer portal.

Acceptance Criteria

• CI step: compare PR branch OpenAPI spec against main branch spec using openapi-diff
• Breaking change detection: removed endpoints, removed fields, changed types (string->number), added required fields
• Change categorization: breaking (major version), additive (minor), deprecation (patch)
• Changelog entry: auto-generated markdown with endpoint path, HTTP method, change description, migration guide link
• PR comment: GitHub Action bot posts changelog preview on PR
• Publish: on release, append to developer-portal/docs/changelog/ page
• Edge case: no OpenAPI changes (skip changelog generation)
• Edge case: multiple OpenAPI spec files (aggregate all diffs)

Technical Scope

• scripts/api-changelog.sh - changelog generation script
• .github/workflows/changelog-check.yml - PR changelog check and comment
• developer-portal/docs/changelog/ - published changelog pages
• packages/openapi-diff/ - diff utility wrapper
• backend/shared/openapi/ - spec validation helper

[Glittersup]

@Glittersup has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I’m interested in handling this issue. I’ve built and tested web3 applications across contracts, backend services, and frontend flows.

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

[drips-wave]

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

🧑‍💻 @Emickclone: 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

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊