feat - Implement Pet Update Endpoint

[System-Garcia]

Resolves #22

Acceptance Criteria:

• Pet profile updates can only be performed by the pet's owner, with ownership verification implemented.
• Input data for updates is validated to ensure it meets specified criteria.
• The endpoint supports both partial and full updates of pet profiles.
• Only authenticated and authorized users are able to update pet profiles.
• Appropriate feedback/error messages are returned if the update attempt fails due to reasons like unauthorized access, invalid data, or other issues.