add required properties to multi-module schema (#15496)

collectors/metadata/schemas/multi-module.json

@@ -1,16 +1,20 @@
 {
-    "$schema": "http://json-schema.org/draft-07/schema#",
-    "type": "object",
-    "properties": {
-        "plugin_name": {
-            "type": "string"
-        },
-        "modules": {
-            "type": "array",
-            "description": "A list of single module templates",
-            "items": {
-                "$ref": "./single-module.json"
-            }
-        }
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "type": "object",
+  "properties": {
+    "plugin_name": {
+      "type": "string"
+    },
+    "modules": {
+      "type": "array",
+      "description": "A list of single module templates",
+      "items": {
+        "$ref": "./single-module.json"
+      }
     }
-}
+  },
+  "required": [
+    "plugin_name",
+    "modules"
+  ]
+}