Avoid roundtrip to string by serializing directly to UTF-8 bytes

Author: 0xced

src/Docker.DotNet/Endpoints/ImageOperations.cs

@@ -5,7 +5,6 @@
 using System.Linq;
 using System.Net;
 using System.Net.Http;
-using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -307,9 +306,7 @@ private Dictionary<string, string> RegistryAuthHeaders(AuthConfig authConfig)
             {
                 {
                     RegistryAuthHeaderKey,
-                    Convert.ToBase64String(
-                        Encoding.UTF8.GetBytes(
-                            this._client.JsonSerializer.SerializeObject(authConfig ?? new AuthConfig())))
+                    Convert.ToBase64String(this._client.JsonSerializer.SerializeObject(authConfig ?? new AuthConfig()))
                     .Replace("/", "_").Replace("+", "-") 
                     // This is not documented in Docker API but from source code (https://github.com/docker/docker-ce/blob/10e40bd1548f69354a803a15fde1b672cc024b91/components/cli/cli/command/registry.go#L47)
                     // and from multiple internet sources it has to be base64-url-safe. 
@@ -325,7 +322,7 @@ private Dictionary<string, string> RegistryConfigHeaders(IEnumerable<AuthConfig>
             {
                 {
                     RegistryConfigHeaderKey,
-                    Convert.ToBase64String(Encoding.UTF8.GetBytes(this._client.JsonSerializer.SerializeObject(configDictionary)))
+                    Convert.ToBase64String(this._client.JsonSerializer.SerializeObject(configDictionary))
                 }
             };
         }

src/Docker.DotNet/Endpoints/SwarmOperations.cs

@@ -4,7 +4,6 @@ namespace Docker.DotNet
     using System.Collections.Generic;
     using System.Net;
     using System.Net.Http;
-    using System.Text;
     using System.Threading.Tasks;
     using System.Threading;
     using Models;
@@ -226,7 +225,7 @@ private IDictionary<string, string> RegistryAuthHeaders(AuthConfig authConfig)
             {
                 {
                     "X-Registry-Auth",
-                    Convert.ToBase64String(Encoding.UTF8.GetBytes(this._client.JsonSerializer.SerializeObject(authConfig)))
+                    Convert.ToBase64String(this._client.JsonSerializer.SerializeObject(authConfig))
                 }
             };
         }

src/Docker.DotNet/JsonSerializer.cs

@@ -68,9 +68,9 @@ public T DeserializeObject<T>(string json)
             return System.Text.Json.JsonSerializer.Deserialize<T>(json, _options);
         }
 
-        public string SerializeObject<T>(T value)
+        public byte[] SerializeObject<T>(T value)
         {
-            return System.Text.Json.JsonSerializer.Serialize(value, _options);
+            return System.Text.Json.JsonSerializer.SerializeToUtf8Bytes(value, _options);
         }
 
         public JsonContent GetHttpContent<T>(T value)