Fix #30915: add warning for deprecated social auth

Author: LEDfan

src/main/java/eu/openanalytics/containerproxy/auth/impl/SocialAuthenticationBackend.java

@@ -20,6 +20,8 @@
  */
 package eu.openanalytics.containerproxy.auth.impl;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.annotation.web.configurers.ExpressionUrlAuthorizationConfigurer.AuthorizedUrl;
@@ -33,6 +35,15 @@
 public class SocialAuthenticationBackend implements IAuthenticationBackend {
 
 	public static final String NAME = "social";
+
+	public SocialAuthenticationBackend() {
+		Logger logger = LoggerFactory.getLogger(getClass());
+		logger.warn("WARNING: ###");
+		logger.warn("WARNING: ###");
+		logger.warn("WARNING: Social authentication is deprecated and will be removed in the next version (3.1.0)!");
+		logger.warn("WARNING: ###");
+		logger.warn("WARNING: ###");
+	}
 
 	@Override
 	public String getName() {