`RefreshTokenOAuth2AuthorizedClientProvider` initialization slows down application startup

[AB-xdev]

Describe the bug

During application startup RefreshTokenOAuth2AuthorizedClientProvider is created by org.springframework.security.config.annotation.web.configuration.OAuth2ClientConfiguration.OAuth2AuthorizedClientManagerRegistrar#getRefreshTokenAuthorizedClientProvider

and because of

spring-security/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/RefreshTokenOAuth2AuthorizedClientProvider.java

Line 53 in 9161ece

private OAuth2AccessTokenResponseClient<OAuth2RefreshTokenGrantRequest> accessTokenResponseClient = new RestClientRefreshTokenTokenResponseClient();

it requires quite some time (300ms; ~3% of my application startup time is spent there) to initialize because it creates a HttpClient:

Currently it's not possible in any way to disable this behavior because

• There is no constructor of RefreshTokenOAuth2AuthorizedClientProvider that leaves accessTokenResponseClient empty
• The classes can't be overriden/proxied because they are all declared final
  • I'm not sure why this is the case because OAuth2AuthorizedClientManagerRegistrar#getAuthorizedClientProviderByType checks for subclasses of this type which is impossible when they have been declared final

To Reproduce
N/A see code above

Expected behavior

• Create a constructor of RefreshTokenOAuth2AuthorizedClientProvider that does not initialize accessTokenResponseClient
• Make RefreshTokenOAuth2AuthorizedClientProvider not final so that users can provide their custom implementations. This should be done for all classes that implement OAuth2AuthorizedClientProvider
• Maybe initialize the default RestClientRefreshTokenTokenResponseClient on a background thread if available to not slow down the application start

Sample

Already described above