Refactor Receiver handling to use ReceiverVM

Updated ReceiverModel and EnvelopeEditorController to utilize ReceiverVM instead of Receiver in multiple function signatures. This change enhances the structure and flexibility of receiver data handling. Adjusted related methods in frmEnvelopeEditor to align with the new view model approach.

EnvelopeGenerator.CommonServices/Models/ReceiverModel.vb

@@ -37,7 +37,7 @@ Public Class ReceiverModel
         }
     End Function
 
-    Public Function Insert(pReceiver As Receiver, pTransaction As SqlTransaction) As Boolean
+    Public Function Insert(pReceiver As ReceiverVM, pTransaction As SqlTransaction) As Boolean
         Dim oSignature As String = pReceiver.GetSignature()
         Dim oCheck = $"SELECT COUNT(GUID) FROM [dbo].[TBSIG_RECEIVER] WHERE SIGNATURE = '{oSignature}'"
         Dim oExists = Database.GetScalarValue(oCheck)
@@ -157,7 +157,7 @@ Public Class ReceiverModel
         End Try
     End Function
 
-    Public Function ListReceivers(pReceiversFromGrid As List(Of Receiver)) As IEnumerable(Of Receiver)
+    Public Function ListReceivers(pReceiversFromGrid As List(Of ReceiverVM)) As IEnumerable(Of Receiver)
         Try
             If pReceiversFromGrid.Count = 0 Then
                 Return New List(Of Receiver)