Update WireMockProtoFileResolver and add tests for ProtoBufUtils (#1252)

* Update WireMockProtoFileResolver and add tests for ProtoBufUtils

* .

test/WireMock.Net.Tests/Grpc/ProtoBufUtilsTests.cs

@@ -0,0 +1,41 @@
+// Copyright © WireMock.Net
+
+#if PROTOBUF
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using FluentAssertions;
+using WireMock.Util;
+using Xunit;
+
+namespace WireMock.Net.Tests.Grpc;
+
+public class ProtoBufUtilsTests
+{
+    [Fact]
+    public async Task GetProtoBufMessageWithHeader_MultipleProtoFiles()
+    {
+        // Arrange
+        var greet = await ReadProtoFileAsync("greet1.proto");
+        var request = await ReadProtoFileAsync("request.proto");
+
+        // Act
+        var responseBytes = await ProtoBufUtils.GetProtoBufMessageWithHeaderAsync(
+            [greet, request],
+            "greet.HelloRequest",
+            new
+            {
+                name = "hello"
+            }
+        );
+
+        // Assert
+        Convert.ToBase64String(responseBytes).Should().Be("AAAAAAcKBWhlbGxv");
+    }
+
+    private static Task<string> ReadProtoFileAsync(string filename)
+    {
+        return File.ReadAllTextAsync(Path.Combine(Directory.GetCurrentDirectory(), "Grpc", filename));
+    }
+}
+#endif