Fix build warnings

Author: GarrettBeatty

Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/ApiGatewayRequestTranslatorFactory.cs

@@ -28,7 +28,8 @@ public IApiGatewayRequestTranslator Create(ApiGatewayMode apiGatewayMode)
             {
                 ApiGatewayMode.REST => _serviceProvider.GetRequiredService<ApiGatewayProxyRequestTranslator>(),
                 ApiGatewayMode.HTTPV1 => _serviceProvider.GetRequiredService<ApiGatewayProxyRequestTranslator>(),
-                ApiGatewayMode.HTTPV2 => _serviceProvider.GetRequiredService<ApiGatewayHttpApiV2ProxyRequestTranslator>()
+                ApiGatewayMode.HTTPV2 => _serviceProvider.GetRequiredService<ApiGatewayHttpApiV2ProxyRequestTranslator>(),
+                _ => throw new NotImplementedException()
             };
         }
     }

Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/HttpRequestUtility.cs

@@ -56,8 +56,8 @@ public string ReadRequestBody(HttpRequest request)
 
             foreach (var header in headers)
             {
-                singleValueHeaders[header.Key] = header.Value.Last();
-                multiValueHeaders[header.Key] = header.Value.ToList();
+                singleValueHeaders[header.Key] = header.Value.Last() ?? "";
+                multiValueHeaders[header.Key] = [.. header.Value];
             }
 
             return (singleValueHeaders, multiValueHeaders);
@@ -82,7 +82,7 @@ public string ReadRequestBody(HttpRequest request)
 
             foreach (var param in query)
             {
-                singleValueParams[param.Key] = param.Value.Last();
+                singleValueParams[param.Key] = param.Value.Last() ?? "";
                 multiValueParams[param.Key] = [.. param.Value];
             }