WebFluxSecurityConfiguration does not configure oauth2Client

[mbhave]

In Spring Boot, for the servlet case, the auto-configuration configures both oauth2Login and oauth2Client. If there's a reason for not configuring oauth2Client in Spring Security for the reactive case, we should look at aligning things in Boot's auto-configuration.

[jgrandja]

Thanks @mbhave.
I've updated WebFluxSecurityConfiguration to be consistent with the defaults in OAuth2WebSecurityConfiguration.OAuth2WebSecurityConfigurerAdapter.