Update Sender role constant to "EGSender"

Changed the value of the Sender constant in the Role class from "Sender" to "EGSender" to ensure consistency with updated naming conventions.

EnvelopeGenerator.Domain/Constants/Role.cs

@@ -18,6 +18,6 @@ namespace EnvelopeGenerator.Domain.Constants
             public const string FullyAuth = "FullyAuth";
         }
 
-        public const string Sender = "Sender";
+        public const string Sender = "EGSender";
     }
 }