Add ability to customize OAuth2AuthorizationRequestRedirectWebFilter in OAuth2LoginSpec

[rchigvintsev]

It would be nice to be able to customize OAuth2AuthorizationRequestRedirectWebFilter during configuring of OAuth2 login in the following way: http.oauth2Login().authorizationRequestRepository(requestRepository) .

Also for now OAuth2AuthorizationRequestRedirectWebFilter creates its own instance of ServerRequestCache. I think common ServerRequestCache (that is configured using RequestCacheSpec) should be used in this case.