Feature/cancel initial subscriptions

Add the cancel_subscription workflow that allows for taking a subscription from INITIAL to TERMINATED.

Since it's a termination workflow, we can't change this from showing up differently (they're forcefully all called "Terminate router" in this case). But only one is available to run, so I'd say this is acceptable.

Also, I added some subtile warnings to prevent accidentally running this.

gso/migrations/versions/2024-03-21_734e36a3e70b_add_subscription_cancellation_workflow.py

+"""Add subscription cancellation workflow.
+
+Revision ID: 734e36a3e70b
+Revises: d61c0f92da1e
+Create Date: 2024-03-21 13:03:08.981028
+
+"""
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = '734e36a3e70b'
+down_revision = 'd61c0f92da1e'
+branch_labels = None
+depends_on = None
+
+
+from orchestrator.migrations.helpers import add_products_to_workflow_by_product_tag, create_workflow, delete_workflow, remove_products_from_workflow_by_product_tag
+
+
+products = ["RTR", "IPTRUNK"]
+new_workflows = [
+    {
+        "name": "cancel_subscription",
+        "target": "TERMINATE",
+        "description": "Cancel a subscription",
+        "product_type": "Site"
+    }
+]
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+    for workflow in new_workflows:
+        create_workflow(conn, workflow)
+    for product_tag in products:
+        add_products_to_workflow_by_product_tag(conn, "cancel_subscription", product_tag)
+
+
+def downgrade() -> None:
+    conn = op.get_bind()
+    for product_tag in products:
+        remove_products_from_workflow_by_product_tag(conn, "cancel_subscription", product_tag)
+    for workflow in new_workflows:
+        delete_workflow(conn, workflow["name"])