GUACAMOLE-393: Add session invalidation hooks to UserContext.

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/sharing/user/SharedUserContext.java

@@ -204,4 +204,9 @@ public class SharedUserContext implements UserContext {
         return Collections.<Form>emptyList();
     }
 
+    @Override
+    public void invalidate() {
+        // Nothing to invalidate
+    }
+
 }

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/user/ModeledUserContext.java

@@ -191,4 +191,9 @@ public class ModeledUserContext extends RestrictedObject
         return ModeledSharingProfile.ATTRIBUTES;
     }
 
+    @Override
+    public void invalidate() {
+        // Nothing to invalidate
+    }
+
 }

extensions/guacamole-auth-ldap/src/main/java/org/apache/guacamole/auth/ldap/user/UserContext.java

@@ -229,4 +229,9 @@ public class UserContext implements org.apache.guacamole.net.auth.UserContext {
         return Collections.<Form>emptyList();
     }
 
+    @Override
+    public void invalidate() {
+        // Nothing to invalidate
+    }
+
 }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/UserContext.java

@@ -212,4 +212,11 @@ public interface UserContext {
      */
     Collection<Form> getSharingProfileAttributes();
 
+    /**
+     * Invalidates this user context, releasing all associated resources. This
+     * function will be invoked when the user logs out, or when their session
+     * is automatically invalidated.
+     */
+    void invalidate();
+
 }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleUserContext.java

@@ -234,4 +234,9 @@ public class SimpleUserContext implements UserContext {
         return Collections.<Form>emptyList();
     }
 
+    @Override
+    public void invalidate() {
+        // Nothing to invalidate
+    }
+
 }

guacamole/src/main/java/org/apache/guacamole/GuacamoleSession.java

@@ -252,6 +252,10 @@ public class GuacamoleSession {
             }
         }
 
+        // Invalidate all user contextx
+        for (UserContext userContext : userContexts)
+            userContext.invalidate();
+
         // Invalidate the authenticated user object
         authenticatedUser.invalidate();