Adapt UserSession

- Move from App methods to UserSession methods
- Deprecate corresponding App methods

src/Core/Session/Capability/IHandleUserSessions.php

@@ -33,6 +33,13 @@ interface IHandleUserSessions extends IHandleSessions
 	 */
 	public function getLocalUserId();
 
+	/**
+	 * Returns the user nickname of locally logged-in user.
+	 *
+	 * @return string|false User's nickname or false
+	 */
+	public function getLocalUserNickname();
+
 	/**
 	 * Returns the public contact id of logged-in user or false.
 	 *
@@ -79,6 +86,13 @@ interface IHandleUserSessions extends IHandleSessions
 	 */
 	public function isAuthenticated(): bool;
 
+	/**
+	 * Check if current user has admin role.
+	 *
+	 * @return bool true if user is an admin
+	 */
+	public function isSiteAdmin(): bool;
+
 	/**
 	 * Returns User ID of the managed user in case it's a different identity
 	 *