feat: uniform system.content source schema across installers and repositories

tests/content/test_content.yml

@@ -0,0 +1,22 @@
+---
+# Run: ansible-playbook tests/content/test_content.yml
+- name: Content-source fixture tests
+  hosts: localhost
+  gather_facts: false
+  connection: local
+  vars:
+    hypervisor_type: libvirt
+    hypervisor_cfg: { folder: "" }
+  vars_files:
+    - content_fixtures.yml
+  tasks:
+    - name: Load global defaults (system_defaults, content_mirror_defaults, os maps)
+      ansible.builtin.include_vars:
+        file: ../../roles/global_defaults/defaults/main.yml
+
+    - name: Run each content fixture
+      ansible.builtin.include_tasks: _assert_content.yml
+      loop: "{{ content_fixtures }}"
+      loop_control:
+        loop_var: cf
+        label: "{{ cf.name }}"