OAuth2 login url starts with /login/

Fixes gh-4659

config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurer.java

@@ -66,6 +66,7 @@ public final class OAuth2LoginConfigurer<B extends HttpSecurityBuilder<B>> exten
 
 	public OAuth2LoginConfigurer() {
 		super(new AuthorizationCodeAuthenticationFilter(), null);
+		this.authorizationCodeGrantConfigurer.authorizationResponseBaseUri("/login/oauth2/authorize/code");
 	}
 
 	public OAuth2LoginConfigurer<B> clients(ClientRegistration... clientRegistrations) {

config/src/main/java/org/springframework/security/config/oauth2/client/CommonOAuth2Provider.java

@@ -93,7 +93,7 @@ public enum CommonOAuth2Provider {
 		}
 	};
 
-	private static final String DEFAULT_REDIRECT_URL = "{scheme}://{serverName}:{serverPort}{contextPath}/oauth2/authorize/code/{registrationId}";
+	private static final String DEFAULT_REDIRECT_URL = "{scheme}://{serverName}:{serverPort}{contextPath}/login/oauth2/authorize/code/{registrationId}";
 
 	protected final ClientRegistration.Builder getBuilder(String registrationId,
 															ClientAuthenticationMethod method, String redirectUri) {

config/src/test/java/org/springframework/security/config/oauth2/client/CommonOAuth2ProviderTests.java

@@ -31,7 +31,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 public class CommonOAuth2ProviderTests {
 
-	private static final String DEFAULT_REDIRECT_URL = "{scheme}://{serverName}:{serverPort}{contextPath}/oauth2/authorize/code/{registrationId}";
+	private static final String DEFAULT_REDIRECT_URL = "{scheme}://{serverName}:{serverPort}{contextPath}/login/oauth2/authorize/code/{registrationId}";
 
 	@Test
 	public void getBuilderWhenGoogleShouldHaveGoogleSettings() throws Exception {