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

tests/content/content_fixtures.yml

@@ -0,0 +1,78 @@
+---
+# Raw system.content input -> expected normalized system_cfg.content. Covers family
+# source defaults (EL=dvd, else mirror), url pass-through, satellite inputs, and the
+# Arch reflector lock-out (dropped only when a custom mirror url is set).
+content_fixtures:
+  - name: arch-mirror-url-drops-reflector
+    system:
+      os: archlinux
+      content: { url: "https://mirror.internal/archlinux" }
+    expect:
+      source: mirror
+      url: "https://mirror.internal/archlinux"
+    expect_reflector: absent
+
+  - name: arch-no-url-keeps-public-and-reflector
+    system:
+      os: archlinux
+      content: {}
+    expect:
+      source: mirror
+      url: ""
+    expect_reflector: present
+
+  - name: el-mirror-url
+    system:
+      os: almalinux
+      version: "10"
+      content: { source: mirror, url: "https://mirror.internal/almalinux" }
+    expect:
+      source: mirror
+      url: "https://mirror.internal/almalinux"
+
+  - name: el-default-dvd
+    system:
+      os: rhel
+      version: "10"
+      content: {}
+    expect:
+      source: dvd
+      url: ""
+
+  - name: el-satellite-register
+    system:
+      os: almalinux
+      version: "10"
+      content:
+        source: satellite
+        satellite: { host: "sat.internal", org: "SG", activation_key: "ak-el10" }
+    expect:
+      source: satellite
+      url: ""
+      satellite: { host: "sat.internal", org: "SG", activation_key: "ak-el10" }
+
+  - name: debian-default-mirror
+    system:
+      os: debian
+      version: "13"
+      content: {}
+    expect:
+      source: mirror
+      url: "https://deb.debian.org/debian/"
+
+  - name: debian-custom-mirror-lands
+    system:
+      os: debian
+      version: "13"
+      content: { source: mirror, url: "https://mirror.internal/debian" }
+    expect:
+      source: mirror
+      url: "https://mirror.internal/debian"
+
+  - name: ubuntu-default-mirror
+    system:
+      os: ubuntu
+      content: {}
+    expect:
+      source: mirror
+      url: "http://archive.ubuntu.com/ubuntu/"