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/alembic/versions/f7e58d357687_add_has_web_column_to_user.py

@@ -0,0 +1,26 @@
+"""add has_web_login column to user
+
+Revision ID: f7e58d357687
+Revises: bceb1e139447
+Create Date: 2024-09-07 20:20:54.522620
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = "f7e58d357687"
+down_revision = "ba98eba0f66a"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "user",
+        sa.Column("has_web_login", sa.Boolean(), nullable=False, server_default="true"),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("user", "has_web_login")