Add multiple audiences capability to JWT verification

[joshcanhelp]

• Update Auth0Service to allow for array api_audience values
• Add api_client_id config option to add the Client ID to the api_audience value
• Add api_identifier_array config option to define an array of API audiences to allow

This is a non-breaking change that allows the original string definition for jwt_auth.api_identifier to continue working. If you just need to add the Client ID to the allowed audiences, add the new jwt_auth.api_client_id config option like so (using .env variables):

// app/config/config.yml
// ...
jwt_auth:
    domain: '%env(AUTH0_DOMAIN)%'
    authorized_issuer: "https://%env(AUTH0_DOMAIN)%/"
    api_identifier: '%env(AUTH0_AUDIENCE)%'
    api_client_id: '%env(AUTH0_CLIENT_ID)%'
// ...

If you instead want to define an array of audiences to use, do that like so:

// app/config/config.yml
// ...
jwt_auth:
    domain: '%env(AUTH0_DOMAIN)%'
    authorized_issuer: "https://%env(AUTH0_DOMAIN)%/"
    api_identifier_array:
      - '%env(AUTH0_AUDIENCE)%'
      - '%env(AUTH0_CLIENT_ID)%'
      - 'another-api-audience'
// ...

Closes #54

[cocojoe]

👍