GUACAMOLE-1723: Simplify active window check; do not refresh from DB during active sessions.

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

@@ -162,4 +162,9 @@ public class DelegatingUserContext implements UserContext {
         return userContext.getPrivileged();
     }
 
+    @Override
+    public boolean isValid() {
+        return userContext.isValid();
+    }
+
 }

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

@@ -40,6 +40,27 @@ public interface UserContext {
      */
     User self();
 
+    /**
+     * Returns true if the session for the User associated with this user
+     * context is valid, or false otherwise. If the session is not valid,
+     * the webapp can be expected to terminate the session within a short
+     * period of time.
+     *
+     * NOTE: The webapp currently checks once a minute, and terminates any
+     * session marked as invalid.
+     *
+     * @return
+     *     true if the session for the User associated with this user
+     *     context is valid, or false otherwise.
+     */
+    default boolean isValid() {
+
+        // A user context is always valid unless explicitly updated by an
+        // implementation
+        return true;
+
+    }
+
     /**
      * Returns an arbitrary REST resource representing this UserContext. The
      * REST resource returned must be properly annotated with JSR-311