Updates the create remote cluster endpoint to require a default team id (#28709)

Support for RemoteClusters without a default team id is in place for
old servers that created those connections before v10.1. This change
forbids the creation of new RemoteClusters without providing this
field, and will be removed when manual invites are implemented.

Co-authored-by: Caleb Roseland <caleb@calebroseland.com>

api/v4/source/remoteclusters.yaml

@@ -86,11 +86,14 @@
               type: object
               required:
                 - name
+                - default_team_id
               properties:
                 name:
                   type: string
                 display_name:
                   type: string
+                default_team_id:
+                  type: string
                 password:
                   type: string
                   description: |