Supporting SQLite and PostreSQL more deliberately

For SQLite, we have to deploy the service as a `StatefulSet` with a bound
`PersistentVolume` holding the SQLite DB, whereas with PostgreSQL, we can
support deployments with multiple replicas.  In that case, we'll migrate with
a separate `Job` instead of attempting to migrate at server startup.

crds.yaml

@@ -20,6 +20,8 @@ spec:
             spec:
               type: object
               properties:
+                version:
+                  type: string
                 sqlite:
                   type: object
                   properties:
@@ -82,6 +84,8 @@ spec:
             spec:
               type: object
               properties:
+                version:
+                  type: string
                 server:
                   type: object
                   properties:

examples/postgres/02-prefect.yaml

@@ -4,6 +4,7 @@ metadata:
   namespace: pop-pg
   name: my-server
 spec:
+  version: 3.0.0rc13
   postgres:
     host: postgres
     port: 5432
@@ -24,6 +25,7 @@ metadata:
   namespace: pop-pg
   name: my-work-pool
 spec:
+  version: 3.0.0rc13
   server:
     namespace: pop-pg
     name: my-server