Addition of audience parameter to oauth config

[danielatk]

The current Oauth configuration contains the following parameters:

• clientId
• clientSecret
• realm
• appName
• scopeSeparator
• additionalQueryStringParams
• useBasicAuthenticationWithAccessCodeGrant
• usePkceWithAuthorizationCodeGrant

The audience parameter is missing from this selection and would be quite useful in many authentication scenarios. Auth0, for example, can only provide a full access token if the audience parameter is received in the request body. This is the same problem raised in this stackoverflow issue, where the only apparent viable solution is to intercept the request and add the audience parameter to the body.

ps: I have already forked. Waiting a review of this to open the PR.