Allow full name to be retrieved by SSO ReverseProxy

Expand on #4585 by also getting the user's full name from the Reverse Proxy:
If a ReverseProxy provides more than REMOTE_USER, such as email, it might
as well also provide the user's full name.

app/Core/Http/Request.php

@@ -291,6 +291,17 @@ class Request extends Base
         return $this->getServerVariable(REVERSE_PROXY_EMAIL_HEADER);
     }
 
+    /**
+     * Get remote user full name
+     *
+     * @access public
+     * @return string
+     */
+    public function getRemoteName()
+    {
+        return $this->getServerVariable(REVERSE_PROXY_FULLNAME_HEADER);
+    }
+
     /**
      * Returns query string
      *