add necessary migration

migrations/versions/2020_022316_f580030d9beb_.py

@@ -0,0 +1,31 @@
+"""empty message
+
+Revision ID: f580030d9beb
+Revises: 903ec5f566e8
+Create Date: 2020-02-23 16:03:46.064813
+
+"""
+import sqlalchemy_utils
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'f580030d9beb'
+down_revision = '903ec5f566e8'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('users', sa.Column('default_mailbox_id', sa.Integer(), nullable=True))
+    op.create_foreign_key(None, 'users', 'mailbox', ['default_mailbox_id'], ['id'])
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_constraint(None, 'users', type_='foreignkey')
+    op.drop_column('users', 'default_mailbox_id')
+    # ### end Alembic commands ###