update model to add migration for use_llm column in assignment_questions

Author: sethbern

migrations/versions/c1d2e3f4a5b6_add_use_llm_to_assignment_questions.py

@@ -0,0 +1,29 @@
+"""add use_llm to assignment_questions
+
+Revision ID: c1d2e3f4a5b6
+Revises: a1b2c3d4e5f6
+Create Date: 2026-04-01 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = 'c1d2e3f4a5b6'
+down_revision: Union[str, None] = 'a1b2c3d4e5f6'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    #Add use_llm column to assignment_questions table as nullable
+    #controls whether a peer instruction question uses an LLM peer for async mode
+    op.add_column('assignment_questions',
+        sa.Column('use_llm', sa.String(length=1), nullable=True)
+    )
+
+
+def downgrade() -> None:
+    op.drop_column('assignment_questions', 'use_llm')