Increase email address length in data models

Updated `ReceiverMail` and `EmailAddress` columns to
support `nvarchar(250)` for longer email addresses.
Retained `[NotMapped]` attribute for `Envelope` in
`EnvelopeReceiverReadOnly.cs` with a note for future
standardization of `EnvelopeId` data type.

EnvelopeGenerator.Domain/Entities/EnvelopeReceiverReadOnly.cs

@@ -23,7 +23,7 @@ namespace EnvelopeGenerator.Domain.Entities
         [NotMapped]
         public Envelope Envelope { get; set; }
 
-        [Column("RECEIVER_MAIL")]
+        [Column("RECEIVER_MAIL", TypeName = "nvarchar(250)")]
         [Required]
         [StringLength(250)]
         [TemplatePlaceholder("NAME_RECEIVER")]

EnvelopeGenerator.Domain/Entities/Receiver.cs

@@ -17,7 +17,8 @@ namespace EnvelopeGenerator.Domain.Entities
         public int Id { get; set; }
 
         [Required, EmailAddress]
-        [Column("EMAIL_ADDRESS", TypeName = "nvarchar(128)")]
+        [Column("EMAIL_ADDRESS", TypeName = "nvarchar(250)")]
+        [StringLength(250)]
         public string EmailAddress { get; set; }
 
         [Required]