Add your favourite oauth2/oidc provider config

[pmlopes]

Currently we ship automatic config for several providers, however this is a very short list:

https://github.com/vert-x3/vertx-auth/blob/master/vertx-auth-oauth2/src/main/java/io/vertx/ext/auth/oauth2/providers/

This task, is about adding config for other providers, for example:

• apple
• attlassian
• auth0
• battlenet
• discord
• gitlab
• identity-server4
• okta
• twitch
• spotify
• yandex
• etc...

The task is about cloning one of the existing providers, for example the github provider:

https://github.com/vert-x3/vertx-auth/blob/master/vertx-auth-oauth2/src/main/java/io/vertx/ext/auth/oauth2/providers/GithubAuth.java

And fill the right values for the provider:

https://github.com/vert-x3/vertx-auth/blob/master/vertx-auth-oauth2/src/main/java/io/vertx/ext/auth/oauth2/providers/GithubAuth.java#L55-L64

The config should be annotated with code comments where the information was found, in order to be fully accepted. For example, when working with GitHub the code should include a comment that the API documentation currently lives in: https://docs.github.com/en/developers/apps/authorizing-oauth-apps so reviewers can verify the code.

Bonus points if you also document the userInfo endpoint with which fields are returned as it would be useful for: #405

[pendula95]

Current build from master is failing on multiple points. Can this be fixed as it makes it hard to test new configured providers.

[pmlopes]

@pendula95 I've triggered a CI build: https://travis-ci.org/github/vert-x3/vertx-auth and it's all green. Perhaps you have an old maven cache?