openapi(api-keys): document reset_usage on update and align examples

[akhilmmenon]

Summary

• Add reset_usage to UpdateApiKeyObject for PUT /api-keys/{id}.
• Document reset_usage as a boolean with clear behavior: resets current usage and can reactivate exhausted keys.
• Add request examples for the update operation, including a minimal payload:
  • {"reset_usage": true}
• Correct update operation curl code samples to use PUT instead of GET.
• Include the OpenAPI changes for the rotate endpoint in this same PR.

Why

The reset usage flow is already supported, but it was not clearly discoverable in the OpenAPI docs for API key updates. This change makes the behavior explicit and provides a minimal testable example.

Merge Timing

This PR should remain open for now. We are waiting to merge it after the rotate endpoint is Generally Available.

Scope Note

Please ensure this PR includes rotate endpoint OpenAPI updates as well (along with the reset_usage documentation updates).

Test Plan

• Validate OpenAPI syntax (redocly lint or equivalent project validation).
• Confirm PUT /api-keys/{id} request schema includes reset_usage.
• Confirm PUT /api-keys/{id} examples include {"reset_usage": true}.
• Confirm update curl examples use -X PUT.
• Confirm rotate endpoint OpenAPI changes are included in this PR.