docs: Add OpenAPI examples for /api/webhooks

[Immaculate0606]

Summary

This PR enhances the OpenAPI documentation for the /api/webhooks endpoint by adding comprehensive example request and response bodies. These examples improve API usability by providing clear reference payloads for consumers and making the generated API documentation more informative.

Closes #740

Changes

• Added example request bodies for /api/webhooks.
• Added example success and error response bodies.
• Ensured examples align with the current API schema and standardized error envelope.
• Updated the OpenAPI specification (src/openapi.yaml) with clear, representative examples.
• Added/updated focused tests to validate the documented schema where applicable.
• Updated documentation to reflect the new API examples.

Testing

• Verified the OpenAPI specification is valid.
• Added focused tests covering the documented changes.
• Confirmed examples conform to the defined request and response schemas.
• Verified linting and formatting compliance.

API Changes

Documentation Update

No functional API changes were introduced. This PR only improves the API documentation by adding example payloads for the /api/webhooks endpoint.

Checklist

• Added OpenAPI request and response examples.
• Added focused tests.
• Updated documentation.
• Follows project linting and code style.
• Maintains standardized error response examples.
• Closes Add OpenAPI examples for /api/webhooks #740

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[greatest0fallt1me]

LGTM — nicely done, thanks for the contribution 🙌