Provide an example using the new Spring Security 5 OAuth 2 implementation

[nanreh]

Looks like a lot has changed with OAuth on the Spring side with Spring Security 5. Would be nice to have an updated example that uses the new approach. I was able to get a simple OAuth Client application working with Spring Boot / Spring Security 5 / and OneLogin... but it's pretty barebones. Linking it here so folks have it since I was unable to find other examples elsewhere.

Link: onelogin-oidc-java-spring-security-5