Add multi-factor auth module setup flow (#16141)

* Add mfa setup flow

* Lint

* Address code review comment

* Fix unit test

* Add assertion for WS response ordering

* Missed a return

* Remove setup_schema from MFA base class

* Move auth.util.validate_current_user -> webscoket_api.ws_require_user

homeassistant/auth/mfa_modules/insecure_example.py

@@ -1,13 +1,13 @@
 """Example auth module."""
 import logging
-from typing import Any, Dict, Optional
+from typing import Any, Dict
 
 import voluptuous as vol
 
 from homeassistant.core import HomeAssistant
 
 from . import MultiFactorAuthModule, MULTI_FACTOR_AUTH_MODULES, \
-    MULTI_FACTOR_AUTH_MODULE_SCHEMA
+    MULTI_FACTOR_AUTH_MODULE_SCHEMA, SetupFlow
 
 CONFIG_SCHEMA = MULTI_FACTOR_AUTH_MODULE_SCHEMA.extend({
     vol.Required('data'): [vol.Schema({
@@ -36,11 +36,18 @@ class InsecureExampleModule(MultiFactorAuthModule):
         return vol.Schema({'pin': str})
 
     @property
-    def setup_schema(self) -> Optional[vol.Schema]:
+    def setup_schema(self) -> vol.Schema:
         """Validate async_setup_user input data."""
         return vol.Schema({'pin': str})
 
-    async def async_setup_user(self, user_id: str, setup_data: Any) -> None:
+    async def async_setup_flow(self, user_id: str) -> SetupFlow:
+        """Return a data entry flow handler for setup module.
+
+        Mfa module should extend SetupFlow
+        """
+        return SetupFlow(self, self.setup_schema, user_id)
+
+    async def async_setup_user(self, user_id: str, setup_data: Any) -> Any:
         """Set up user to use mfa module."""
         # data shall has been validate in caller
         pin = setup_data['pin']