inputs/files: extract source options schema

This is mostly to prepare the support for pipeline options will be
different for pipeline origins than source origins.

inputs/org.osbuild.files

@@ -39,17 +39,22 @@ SCHEMA = r"""
       "type": "string"
     }
   },
-  "object-ref": {
+  "source-options": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {
+      "metadata": {
+        "$ref": "#/definitions/metadata"
+      }
+    }
+  },
+  "source-object-ref": {
     "type": "object",
     "additionalProperties": false,
     "minProperties": 1,
     "patternProperties": {
       ".*": {
-        "type": "object",
-        "additionalProperties": false,
-        "properties": {
-          "metadata": {"$ref": "#/definitions/metadata"}
-        }
+        "$ref": "#/definitions/source-options"
       }
     }
   },
@@ -72,7 +77,7 @@ SCHEMA = r"""
     "description": "Checksums of files to use as files input",
     "oneOf": [
       {"$ref": "#/definitions/plain-ref"},
-      {"$ref": "#/definitions/object-ref"}
+      {"$ref": "#/definitions/source-object-ref"}
     ]
   }
 }