Add unique constraints on some of our tables

I just missed thinking about this originally

alembic/versions/4990a9f1ada3_add_unique_constraints.py

@@ -0,0 +1,28 @@
+"""add unique constraints
+
+Revision ID: 4990a9f1ada3
+Revises: 688af5ecd407
+Create Date: 2016-05-18 15:40:33.511871
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '4990a9f1ada3'
+down_revision = '688af5ecd407'
+branch_labels = None
+depends_on = None
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    op.create_unique_constraint('uq_credit_card_id', 'credit_card', ['card_id'])
+    op.create_unique_constraint('uq_ofxsource_fid', 'ofxsource', ['fid'])
+    op.create_unique_constraint('uq_user_username', 'users', ['username'])
+
+
+def downgrade():
+    op.drop_constraint('uq_user_username', 'users', type_='unique')
+    op.drop_constraint('uq_ofxsource_fid', 'ofxsource', type_='unique')
+    op.drop_constraint('uq_credit_card_id', 'credit_card', type_='unique')