Greenfield: Improve store users API (#6427)

* Greenfield: Improve store users API

- Adds an endpoint to update store users (before they had to be removed ad re-added)
- Checks for the existance of a user and responds with 404 in that case (fixes #6423)
- Allows retrieval of user by user id or email for add and update (consistent with the other endpoints)
- Improves the API docs for the store users endpoints

* Swagger: Reuse UserIdOrEmail parameter component

* Add details to store user data

BTCPayServer.Client/Models/StoreData.cs

@@ -17,7 +17,25 @@ namespace BTCPayServer.Client.Models
         /// </summary>
         public string UserId { get; set; }
 
+        /// <summary>
+        /// the store role of the user
+        /// </summary>
         public string Role { get; set; }
+
+        /// <summary>
+        /// the email AND username of the user
+        /// </summary>
+        public string Email { get; set; }
+        
+        /// <summary>
+        /// the name of the user
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        /// the image url of the user
+        /// </summary>
+        public string ImageUrl { get; set; }
     }
 
     public class RoleData