Update application_roles table for provisioning.

Adds cloud_id and claimed_until columns to the application_roles table
so that rows can be locked when they're being processed and updated with
relevant Azure information when processing is finished. Since the
claimed_until column is now common to a few different models, I've also
moved it to a mixin.

alembic/versions/17da2a475429_add_application_role_cloud_id.py

@@ -0,0 +1,29 @@
+"""add application_role.cloud_id
+
+Revision ID: 17da2a475429
+Revises: 50979d8ef680
+Create Date: 2020-02-01 10:43:03.073539
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = '17da2a475429' # pragma: allowlist secret
+down_revision = '50979d8ef680' # pragma: allowlist secret
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('application_roles', sa.Column('cloud_id', sa.String(), nullable=True))
+    op.add_column('application_roles', sa.Column('claimed_until', sa.TIMESTAMP(timezone=True), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('application_roles', 'cloud_id')
+    op.drop_column('application_roles', 'claimed_until')
+    # ### end Alembic commands ###