Verify token validity

[AntonioRodriguezRuiz]

Feature Description

Create an endpoint to verify the validity of a jwt

Definition of Done

• [x] Implement function happy path
  • [x] Discuss what exactly needs to be returned by this endpoint
• [x] Implement error messages:
  • [x] 400
  • [x] 401 & 403
• [x] #22
• [x] Add OpenAPI docs

[AntonioRodriguezRuiz]

Must return as error codes:

• 200
• 400 (No token provided)
• 401 (Token not valid / expired)