Refactor Envelope properties; add DefaultDocument property

Refactored property declarations in the Envelope class for improved readability by removing unnecessary line breaks and nullable preprocessor directives. Added a [NotMapped] DefaultDocument property to return the first document in the Documents list, or null if none exist.

EnvelopeGenerator.Domain/Entities/Envelope.cs

@@ -154,8 +154,7 @@ namespace EnvelopeGenerator.Domain.Entities
 #if nullable
         ?
 #endif
-            Type
+            Type { get; set; }
-        { get; set; }
 
 #if NETFRAMEWORK
         [NotMapped]
@@ -169,22 +168,26 @@ namespace EnvelopeGenerator.Domain.Entities
 #if nullable
         ?
 #endif
-            Documents
+            Documents { get; set; }
-        { get; set; }
+
+        [NotMapped]
+        public Document
+#if nullable
+        ?
+#endif
+            DefaultDocument => Documents?.FirstOrDefault();
 
         public List<History>
 #if nullable
         ?
 #endif
-            Histories
+            Histories { get; set; }
-        { get; set; }
 
         public List<EnvelopeReceiver>
 #if nullable
         ?
 #endif
-            EnvelopeReceivers
+            EnvelopeReceivers { get; set; }
-        { get; set; }
 
         //#if NETFRAMEWORK
         /// <summary>