Add KYC-Fill-In examples for consent collection, access token requests and API use

[AxelNennker]

What type of PR is this?

• documentation

What this PR does / why we need it:

This PR shows:

• how user consent can be requested using OIDC authorization code flow
• the use of kyc-fill-in:set-all when requesting an OIDC code
• explains that the subject identifier for the API is associated with the access token
• explains that the scopes for the API is associated with the access token

No extra phoneNumber request parameter is needed when using 3-legged / front-end flow.
Using an extra phoneNumber parameter in the API request should be restricted to 2-legged flow.