require that responses object has 'default' or a response code (fixes #2833)

ref: https://spec.openapis.org/oas/v3.1.0#responses-object

Author: karenetheridge

schemas/v3.1/schema.json

@@ -840,7 +840,16 @@
       },
       "minProperties": 1,
       "$ref": "#/$defs/specification-extensions",
-      "unevaluatedProperties": false
+      "unevaluatedProperties": false,
+      "$comment": "either default, or at least one response code property must exist",
+      "if": {
+        "patternProperties": {
+          "^[1-5](?:[0-9]{2}|XX)$": false
+        }
+      },
+      "then" : {
+        "required": [ "default" ]
+      }
     },
     "response": {
       "$comment": "https://spec.openapis.org/oas/v3.1.0#response-object",

schemas/v3.1/schema.yaml

@@ -574,6 +574,12 @@ $defs:
     minProperties: 1
     $ref: '#/$defs/specification-extensions'
     unevaluatedProperties: false
+    $comment: either default, or at least one response code property must exist
+    if:
+      patternProperties:
+        '^[1-5](?:[0-9]{2}|XX)$': false
+    then:
+      required: [default]
 
   response:
     $comment: https://spec.openapis.org/oas/v3.1.0#response-object