added mails page + reworked button placement

BetterIServ.Backend/Entities/Credentials.cs

@@ -1,7 +1,8 @@
 namespace BetterIServ.Backend.Entities; 
 
-public struct Credentials {
-    public string Domain { get; set; }
-    public string Username { get; set; }
-    public string Password { get; set; }
+public class Credentials {
+    public string? Domain { get; set; }
+    public string? Username { get; set; }
+    public string? Password { get; set; }
+    public string? Token { get; set; }
 }

BetterIServ.Backend/Entities/MailContent.cs

@@ -0,0 +1,13 @@
+using Aspose.Email;
+
+namespace BetterIServ.Backend.Entities; 
+
+public struct MailContent {
+    public int Id { get; set; }
+    public MailAddress Sender { get; set; }
+    public string Subject { get; set; }
+    public string Message { get; set; }
+    public DateTime Time { get; set; }
+    public bool Read { get; set; }
+    public string[] Attachments { get; set; }
+}

BetterIServ.Backend/Entities/MailData.cs

@@ -0,0 +1,9 @@
+namespace BetterIServ.Backend.Entities; 
+
+public sealed class MailData : Credentials {
+
+    public string? MailBody { get; set; }
+    public string? Receiver { get; set; }
+    public string? Subject { get; set; }
+    
+}

BetterIServ.Backend/Entities/SingleResult.cs

@@ -0,0 +1,5 @@
+namespace BetterIServ.Backend.Entities; 
+
+public class SingleResult<TValue> {
+    public TValue? Value { get; set; }
+}