dnf.mark: mark packages in DNF state database

This adjustment allows the definition of the mark with the RPMs and runs
DNF after installing the RPMs to put the proper markings in the DNF
state database. See osbuild#455.

This ensures that packages don't get removed during `autoremove` leading
to broken systems.

stages/org.osbuild.dnf.mark

@@ -0,0 +1,46 @@
+#!/usr/bin/python3
+"""
+Mark packages in the DNF state database.
+"""
+
+import sys
+
+from osbuild import api
+
+SCHEMA_2 = """
+"options": {
+  "additionalProperties": false,
+  "properties": {
+    "packages": {
+      "type": "array",
+      "minItems": 1,
+      "description": "Packages and their marks.",
+      "items": {
+        "type": "object",
+        "additionalProperties": false,
+        "properties": {
+          "name": {
+            "type": "string",
+            "description": "Package name."
+          },
+          "mark": {
+            "type": "string",
+            "enum": ["user", "dependency"],
+            "description": "Package mark."
+          }
+        }
+      }
+    }
+  }
+},
+"""
+
+
+def main(tree, inputs, options):
+    return 0
+
+
+if __name__ == "__main__":
+    args = api.arguments()
+    r = main(args["tree"], args["inputs"], args["options"])
+    sys.exit(r)