cloudapi: make Repository.rhsm optional

I think that we can spare the users of clouadpi of writing "rhsm": "false"
into the requests so I decided to make this property optional and default
to false.

This is nice because it matches the behaviour of Weldr repositories and
sources so we can also use test/data/repositories without any changes after
openapi validation is enabled.

Signed-off-by: Ondřej Budai <ondrej@budai.cz>

internal/cloudapi/v2/openapi.v2.yml

@@ -652,11 +652,11 @@ components:
         - vsphere
     Repository:
       type: object
-      required:
-        - rhsm
       properties:
         rhsm:
           type: boolean
+          default: false
+          description: 'Determines whether a valid subscription is required to access this repository.'
         baseurl:
           type: string
           format: url