Additional OAuth 2 providers

We have successfully integrated a single OAuth 2 provider using one of the popular OAuth 2 providers. There are several other providers available; we are going to add a few more providers so our users have more than one option. Spring Security currently supports the Google, GitHub, Facebook, and Okta providers natively. Including additional providers will require configuring custom provider properties.

CommonOAuth2Provider pre-defines a set of default client properties for a number of well-known providers that Spring Security supports natively, as mentioned previously.

For example, the authorization-uri, token-uri, and user-info-uri do not change often for a provider. Therefore, it makes sense to provide default values, to reduce the required configuration.

As demonstrated previously when we configured a Google client, only the client-id and client-secret properties are required.

In order to add GitHub providers to the JBCP calendar application...