Add user when they interact outside of UI (e.g. Slack bot) (#2369)

* Add user when they interact outside of UI (e.g. Slack bot)

* fix mypy errors

* don't use user manager to avoid async messiness

* fix email is none scenario

* fix mypy

* make code slightly clearer

* PR comments

* get slack email in generate button as well

* fix alembic migration

* update name to be more descriptive

---------

Co-authored-by: Hyeong Joon Suh <hyeongjoonsuh@Hyeongs-MacBook-Pro.local>

backend/ee/danswer/server/saml.py

@@ -65,6 +65,7 @@ async def upsert_saml_user(email: str) -> User:
                         password=hashed_pass,
                         is_verified=True,
                         role=role,
+                        has_web_login=True,
                     )
                 )