Consider adding support for requesting refresh_token with offline_access scope

Expected Behavior
I want to add support for the offline_access scope as described in the openid-connect rfc. When the offline_access scope is requested, then a refresh token is issued.

Current Behavior
Currently the spring-authorization-server project issues a refresh token when a RegisteredClient contains AuthorizationGrantType.REFRESH_TOKEN. I would like to change this behavior so that the the client must request the offline_access scope in order for a refresh token to be issued.

Context
What is the best way to add support for this? Initially, I tried copying all of the code from OAuth2AuthorizationCodeAuthenticationProvider into my own custom implementation and edited the conditional statement that determines whether or not refresh token should be issued. However, I would like to avoid copying and overriding this for maintainability reasons. Is there a way to customize this for our implementation? Is this a feature that we could add to directly to the spring-authorization-server project?

Related spring-projects/spring-authorization-server#501 spring-projects/spring-authorization-server#1430

Read oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2AuthorizationCodeAuthenticationProvider.java, especially the conditional at line 216. Review related issues #501 and #1430 for prior context. Done means supporting the offline_access scope so refresh-token issuance follows the requested scope without requiring copied provider code.