Refactor command records and simplify document handling

- Updated `ReceiverGetOrCreateCommand` to include a required `IEnumerable<Signature>`.
- Modified `DocumentCreateCommand` to remove `DataAsByte` and enforce a required `DataAsBase64` property with immutability.
- Cleaned up SQL command formatting in `EnvelopeReceiverAddReadSQL`.
- Simplified document validation logic in `EnvelopeReceiverController` by removing redundant checks.
- Changed hardcoded connection string to a variable `_cnnStr` for improved security and flexibility.

EnvelopeGenerator.GeneratorAPI/Controllers/EnvelopeReceiverController.cs

@@ -221,16 +221,6 @@ public class EnvelopeReceiverController : ControllerBase
             #endregion
 
             #region Add document
-            if(request.Document.DataAsBase64 is null)
-                if (request.Document.DataAsByte is null)
-                    return BadRequest("No document data is found");
-                else
-                    request.Document.DataAsBase64 = Convert.ToBase64String(request.Document.DataAsByte);
-            else if (request.Document.DataAsByte is not null)
-                return BadRequest("Document data cannot be assigned as both byte data and base64 string.");
-            else if (!IsBase64String(request.Document.DataAsBase64))
-                return BadRequest("Document data is not a base64 string");
-
             var document = await _documentExecutor.CreateDocumentAsync(request.Document.DataAsBase64, envelope.Uuid, cancel);
 
             if(document is null)
@@ -279,8 +269,6 @@ public class EnvelopeReceiverController : ControllerBase
             #endregion
 
             #region Create history
-            string connectionString = "Server=YOUR_SERVER;Database=YOUR_DATABASE;Trusted_Connection=True;";
-
             string sql_hist = @"
                 USE [DD_ECM]
 
@@ -294,7 +282,7 @@ public class EnvelopeReceiverController : ControllerBase
 
                 SELECT @OUT_SUCCESS as [@OUT_SUCCESS];";
 
-            using (SqlConnection conn = new(connectionString))
+            using (SqlConnection conn = new(_cnnStr))
             {
                 conn.Open();