Add security to CAMARA_common.yaml

[AxelNennker]

Problem description
OpenAPI Specification allows APIs to describe their authentication and authorization requirements - their security requirements.
This is done by defining a security scheme that can than be applied to endpoints or to the API as a whole.

Commonly used security schemes of a Camara API should be in
CAMARA_common.yaml

Expected action
The IdentityAndConsent WG developed one security scheme for OpenId Connect.

components:
  securitySchemes:
    openId:
      type: openIdConnect
      openIdConnectUrl: https://example.com/.well-known/openid-configuration

This should be added to CAMARA_common.yaml and probably applied to the API as a whole.