Added support retaining body parameter name

src/Microsoft.OpenApi.Readers/V2/OpenApiOperationDeserializer.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.Linq;
+using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Readers.ParseNodes;
@@ -164,6 +165,7 @@ private static OpenApiRequestBody CreateFormBody(ParsingContext context, List<Op
                         {
                             var schema = v.Schema;
                             schema.Description = v.Description;
+                            schema.Extensions = v.Extensions;
                             return schema;
                         }),
                     Required = new HashSet<string>(formParameters.Where(p => p.Required).Select(p => p.Name))
@@ -201,9 +203,11 @@ internal static OpenApiRequestBody CreateRequestBody(
                     v => new OpenApiMediaType
                     {
                         Schema = bodyParameter.Schema
-                    })
+                    }),
+                Extensions = bodyParameter.Extensions
             };
 
+            requestBody.Extensions[OpenApiConstants.BodyName] = new OpenApiString(bodyParameter.Name);
             return requestBody;
         }
 

src/Microsoft.OpenApi/Models/OpenApiConstants.cs

@@ -560,6 +560,11 @@ public static class OpenApiConstants
         /// </summary>
         public const string DefaultDescription = "Default Description";
 
+        /// <summary>
+        /// Field: BodyName extensions
+        /// </summary>
+        public const string BodyName = "x-bodyName";
+
         /// <summary>
         /// Field: version3_0_0
         /// </summary>

src/Microsoft.OpenApi/Models/OpenApiOperation.cs

@@ -241,22 +241,31 @@ public void SerializeAsV2(IOpenApiWriter writer)
                                 Name = property.Key,
                                 Schema = property.Value,
                                 Required = RequestBody.Content.First().Value.Schema.Required.Contains(property.Key)
+
                             });
                     }
                 }
                 else
                 {
                     var content = RequestBody.Content.Values.FirstOrDefault();
+
                     var bodyParameter = new OpenApiBodyParameter
                     {
                         Description = RequestBody.Description,
                         // V2 spec actually allows the body to have custom name.
-                        // Our library does not support this at the moment.
+                        // To allow round-tripping we use an extension to hold the name
                         Name = "body",
                         Schema = content?.Schema ?? new OpenApiSchema(),
-                        Required = RequestBody.Required
+                        Required = RequestBody.Required,
+                        Extensions = RequestBody.Extensions.ToDictionary(k => k.Key, v => v.Value)  // Clone extensions so we can remove the x-bodyName extensions from the output V2 model.
                     };
 
+                    if (bodyParameter.Extensions.ContainsKey(OpenApiConstants.BodyName))
+                    {
+                        bodyParameter.Name = (RequestBody.Extensions[OpenApiConstants.BodyName] as OpenApiString)?.Value ?? "body";
+                        bodyParameter.Extensions.Remove(OpenApiConstants.BodyName);
+                    }
+
                     parameters.Add(bodyParameter);
                 }
             }

test/Microsoft.OpenApi.Readers.Tests/V2Tests/OpenApiOperationTests.cs

@@ -7,6 +7,7 @@
 using FluentAssertions;
 using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
+using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Readers.ParseNodes;
 using Microsoft.OpenApi.Readers.V2;
@@ -180,6 +181,9 @@ public class OpenApiOperationTests
                             Type = "object"
                         }
                     }
+                },
+                Extensions = { 
+                    [OpenApiConstants.BodyName] = new OpenApiString("petObject") 
                 }
             },
             Responses = new OpenApiResponses