Update to final draft 0.1: /token

[barroco]

Client mode

https://github.com/ebu/cpa-spec/blob/draft-1.0/etsi-specification.md#access-token-request

• Add scope
• Remove service_provider

User mode

https://github.com/ebu/cpa-spec/blob/draft-1.0/etsi-specification.md#access-token-request-1

• Remove code
• Add client_secret

Response

https://github.com/ebu/cpa-spec/blob/draft-1.0/etsi-specification.md#access-token-response-1

Success

• Add description
• Add short_description
• Add scope

Pending

• Change status code to 202

Error

• Add slow_down
• Add expired