feat(openai): 新增文件上传相关接口

src/SKIT.FlurlHttpClient.Wechat.OpenAI/Extensions/WechatOpenAIClientExecuteFileExtensions.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Web;
+using Flurl;
+using Flurl.Http;
+
+namespace SKIT.FlurlHttpClient.Wechat.OpenAI
+{
+    public static class WechatOpenAIClientExecuteFileExtensions
+    {
+        /// <summary>
+        /// <para>异步调用 [POST] /v1/file/upload 接口。</para>
+        /// <para>REF: https://developers.weixin.qq.com/doc/aispeech/openapi/api/v1/file_upload.html </para>
+        /// </summary>
+        /// <param name="client"></param>
+        /// <param name="request"></param>
+        /// <param name="cancellationToken"></param>
+        /// <returns></returns>
+        public static async Task<Models.FileUploadResponse> ExecuteFileUploadAsync(this WechatOpenAIClient client, Models.FileUploadRequest request, CancellationToken cancellationToken = default)
+        {
+            if (client is null) throw new ArgumentNullException(nameof(client));
+            if (request is null) throw new ArgumentNullException(nameof(request));
+
+            if (request.FileName == null)
+                request.FileName = Guid.NewGuid().ToString("N").ToLower() + ".csv";
+
+            if (request.FileContentType == null)
+                request.FileContentType = "text/csv";
+
+            IFlurlRequest flurlReq = client
+                .CreateRequest(request, HttpMethod.Post, "v1", "file", "upload");
+
+            using var fileContent = new ByteArrayContent(request.FileBytes ?? new byte[0]);
+            using var httpContent = new MultipartFormDataContent();
+            httpContent.Add(fileContent, "\"file\"", $"\"{HttpUtility.UrlEncode(request.FileName)}\"");
+            fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse(request.FileContentType);
+            fileContent.Headers.ContentLength = request.FileBytes?.Length;
+
+            return await client.SendRequestAsync<Models.FileUploadResponse>(flurlReq, httpContent: httpContent, cancellationToken: cancellationToken);
+        }
+    }
+}