Spring Security Document parameters converter in oauth2 client servlet docs

Servlet documentation should mention how to provide a custom parameters converter to override parameters of an OAuth 2.0 Access Token Request: * AbstractOAuth2AuthorizationGrantRequestEntityConverter.setParametersConverter(). * AbstractOAuth2AuthorizationGrantRequestEntityConverter.addParametersConverter().

Currently, only reactive documentation mentions this capability (in AbstractWebClientReactiveOAuth2AccessTokenResponseClient).

Comment From: sjohnr

Moved to 5.6.1 milestone, as this missed the 5.6.0 release notes.