Migration to add folder_permissions to invited_users table

Added a new JSONB column, folder_permissions, to the invited_users table
to store a list of folders that an invited user can see. This is
nullable for now, but will be changed to be non-nullable and
back-populated later.

migrations/versions/0280_invited_user_folder_perms.py

@@ -0,0 +1,21 @@
+"""
+
+Revision ID: 0280_invited_user_folder_perms
+Revises: 0279_remove_fk_to_users
+Create Date: 2019-03-11 14:38:28.010082
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision = '0280_invited_user_folder_perms'
+down_revision = '0279_remove_fk_to_users'
+
+
+def upgrade():
+    op.add_column('invited_users', sa.Column('folder_permissions', postgresql.JSONB(none_as_null=True, astext_type=sa.Text()), nullable=True))
+
+
+def downgrade():
+    op.drop_column('invited_users', 'folder_permissions')