User: Add name and image URL (#6008)

* User: Add name and image URL

More personalization options, prerequisite for btcpayserver/app#3.

Additionally:
- Remove ambigious and read-only username from manage view.
- Improve email verification conditions and display.
- Greenfield: Update current user. Prerequisite for btcpayserver/app#13.

* Refactor UpdateCurrentUser

* Replace new columns by UserBlob

* Update email check and add test case for mailbox addresses

---------

Co-authored-by: nicolas.dorier <nicolas.dorier@gmail.com>

BTCPayServer.Client/Models/CreateApplicationUserRequest.cs

@@ -2,6 +2,16 @@ namespace BTCPayServer.Client.Models
 {
     public class CreateApplicationUserRequest
     {
+        /// <summary>
+        /// the name of the new user
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        /// the image url of the new user
+        /// </summary>
+        public string ImageUrl { get; set; }
+
         /// <summary>
         /// the email AND username of the new user
         /// </summary>