Create Model\Register

- Add Model\User::exists method

src/Model/User.php

@@ -31,6 +31,17 @@ require_once 'include/text.php';
  */
 class User
 {
+	/**
+	 * Returns true if a user record exists with the provided id
+	 *
+	 * @param  integer $uid
+	 * @return boolean
+	 */
+	public static function exists($uid)
+	{
+		return DBA::exists('user', ['uid' => $uid]);
+	}
+
 	/**
 	 * @brief Returns the user id of a given profile url
 	 *