Migrate postage into templates_history table

migrations/versions/0256_set_postage_tmplt_hstr.py

@@ -0,0 +1,28 @@
+"""
+
+Revision ID: 0256_set_postage_tmplt_hstr
+Revises: 0255_another_letter_org
+Create Date: 2019-02-05 14:51:30.808067
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '0256_set_postage_tmplt_hstr'
+down_revision = '0255_another_letter_org'
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.execute(
+        """UPDATE templates_history SET postage = services.postage
+        FROM services WHERE template_type = 'letter' AND service_id = services.id"""
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.execute("UPDATE templates_history SET postage = null WHERE template_type = 'letter'")
+    # ### end Alembic commands ###