add user_corpus m2m relationship

migrations/versions/4aa88f253dab_.py

@@ -0,0 +1,31 @@
+"""Add corpus_followers table
+
+Revision ID: 4aa88f253dab
+Revises: 5b2a6e590166
+Create Date: 2023-01-12 14:47:39.492875
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '4aa88f253dab'
+down_revision = '5b2a6e590166'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        'corpus_followers',
+        sa.Column('user_id', sa.Integer(), nullable=False),
+        sa.Column('corpus_id', sa.Integer(), nullable=False),
+        sa.ForeignKeyConstraint(['corpus_id'], ['corpora.id'], ),
+        sa.ForeignKeyConstraint(['user_id'], ['users.id'], ),
+        sa.PrimaryKeyConstraint('user_id', 'corpus_id')
+    )
+
+
+def downgrade():
+    op.drop_table('corpus_followers')