Changes failed Graph batch response to 200 OK. Closes #1358 (#1359)

Author: waldekmastykarz

DevProxy.Abstractions/Models/GraphBatchRequestPayload.cs

@@ -12,6 +12,7 @@ public class GraphBatchRequestPayload
 public class GraphBatchRequestPayloadRequest
 {
     public object? Body { get; set; }
+    public IEnumerable<string>? DependsOn { get; set; }
 #pragma warning disable CA2227
     public Dictionary<string, string>? Headers { get; set; } = [];
 #pragma warning restore CA2227

DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs

@@ -234,8 +234,12 @@ private void FailBatch(ProxyRequestArgs e)
             try
             {
                 // pick a random error response for the current request method
+                // if the request has dependencies, use FailedDependency status code
+                // https://learn.microsoft.com/en-us/graph/json-batching?tabs=http#sequencing-requests-with-the-dependson-property
                 var methodStatusCodes = _methodStatusCode[request.Method];
-                var errorStatus = methodStatusCodes[_random.Next(0, methodStatusCodes.Length)];
+                var errorStatus = request.DependsOn is not null && request.DependsOn.Any() ?
+                    HttpStatusCode.FailedDependency :
+                    methodStatusCodes[_random.Next(0, methodStatusCodes.Length)];
 
                 var response = new GraphBatchResponsePayloadResponse
                 {
@@ -315,8 +319,8 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
 
     private void UpdateProxyBatchResponse(ProxyRequestArgs ev, GraphBatchResponsePayload response)
     {
-        // failed batch uses a fixed 424 error status code
-        var errorStatus = HttpStatusCode.FailedDependency;
+        // failed batch uses 200 OK status code
+        var errorStatus = HttpStatusCode.OK;
 
         var session = ev.Session;
         var requestId = Guid.NewGuid().ToString();