Frontend indicate require admin (#22272)

* Allow panels to indicate they are meant for admins

* Panels to indicate when they require admin access

* Do not return admin-only panels to non-admin users

* Fix flake8

tests/components/panel_custom/test_init.py

@@ -130,6 +130,7 @@ async def test_module_webcomponent(hass):
             },
             'embed_iframe': True,
             'trust_external_script': True,
+            'require_admin': True,
         }
     }
 
@@ -145,6 +146,7 @@ async def test_module_webcomponent(hass):
 
     panel = panels['nice_url']
 
+    assert panel.require_admin
     assert panel.config == {
         'hello': 'world',
         '_panel_custom': {