Refactor envelope and history query structures

- Removed `Sender` parameter and properties from `EnvelopeQuery`.
- Deleted `SenderQuery` class entirely.
- Cleaned up `HistoryQuery` by removing unused `using` directives and `ReferenceType` logic.
- Added `Related` parameter to `ReadHistoryQuery` for reference type indication.
- Updated `ReferenceType` enum in `Constants.vb` to use explicit integer values.
- Modified `HistoryController` to utilize the new `Related` property for determining sender/receiver inclusion.

EnvelopeGenerator.GeneratorAPI/Controllers/HistoryController.cs

@@ -70,11 +70,10 @@ public class HistoryController : ControllerBase
     [Authorize]
     public async Task<IActionResult> GetAllAsync([FromQuery] ReadHistoryQuery history)
     {
-        ReferenceType? refTypEnum = history.ReferenceType;
         bool withReceiver = false;
         bool withSender = false;
 
-        switch (refTypEnum)
+        switch (history.Related)
         {
             case ReferenceType.Receiver:
                 withReceiver = true;
@@ -86,7 +85,7 @@ public class HistoryController : ControllerBase
 
         var histories = await _service.ReadAsync(
             envelopeId: history.EnvelopeId,
-            referenceType: refTypEnum,
+            referenceType: history.Related,
             withSender: withSender,
             withReceiver: withReceiver);