fix HTTP response generator methods

HTTP/HttpFields.cs

@@ -173,6 +173,8 @@ public record HttpFields
     }
 }
 
+public delegate void FieldCallback(string name, string value);
+
 public enum ConnectionType
 {
     Close,

HTTP/HttpResponse.cs

@@ -25,27 +25,23 @@ public class SwitchingProtocols : HttpResponse
 /// </summary>
 public class HttpResponse
 {
-    public static HttpResponse OK(HttpContent? content) => new HttpResponse(200, "OK", content);
+    public static HttpResponse OK(HttpContent? content = null) => new HttpResponse(200, "OK", content);
 
     public static HttpResponse Redirect(string location) => new HttpResponse(301, "Redirect", new HttpFields() { Location = location });
 
-    public static HttpResponse BadRequest(HttpContent? content) => new HttpResponse(400, "Bad request", content);
+    public static HttpResponse BadRequest(HttpContent? content = null) => new HttpResponse(400, "Bad request", content);
 
-    public static HttpResponse NotFound(HttpContent? content) => new HttpResponse(404, "Not found", content);
+    public static HttpResponse NotFound(HttpContent? content = null) => new HttpResponse(404, "Not found", content);
 
-    public static HttpResponse NotAcceptable(HttpContent? content) => new HttpResponse(406, "Not acceptable", content);
+    public static HttpResponse NotAcceptable(HttpContent? content = null) => new HttpResponse(406, "Not acceptable", content);
 
-    public static HttpResponse InternalServerError(string location) => new HttpResponse(500, "Internal server error");
+    public static HttpResponse InternalServerError(HttpContent? content = null) => new HttpResponse(500, "Internal server error", content);
+
+    public static implicit operator HttpResponse(HttpContent value) => OK(value);
+
+    public static implicit operator HttpResponse(HttpContent? value) => value == null ? NotFound(value) : OK(value);
 
-    public static implicit operator HttpResponse(HttpContent value)
-    {
-        return OK(value);
-    }
 
-    public static implicit operator HttpResponse(HttpContent? value)
-    {
-        return value == null ? NotFound(value) : OK(value);
-    }
 
     public readonly int StatusCode;
 
@@ -115,6 +111,4 @@ public class HttpResponse
 
         await stream.Flush();
     }
-}
+}
-
-public delegate void FieldCallback(string name, string value);