Make response headers required

Author: verdie-g

src/JsonApiDotNetCore.OpenApi/SwaggerComponents/JsonApiOperationDocumentationFilter.cs

@@ -441,6 +441,7 @@ private static void SetResponseHeaderETag(OpenApiResponses responses, HttpStatus
         response.Headers[HeaderNames.ETag] = new OpenApiHeader
         {
             Description = "ETag identifying the version of the fetched resource.",
+            Required = true,
             Example = new OpenApiString("\"33a64df551425fcc55e4d42a148795d9f25f89d4\""),
         };
     }
@@ -451,6 +452,7 @@ private static void SetResponseHeaderLocation(OpenApiResponses responses, HttpSt
         response.Headers[HeaderNames.Location] = new OpenApiHeader
         {
             Description = "Location of the newly created resource.",
+            Required = true,
         };
     }