Refactor enum handling in MemoryCache and HistoryController

Updated `GetEnumAsDictionary<TEnum>` in `MemoryCacheExtensions.cs` to use a loop for populating a dictionary of enum values, removing LINQ for simplicity.

Modified `HistoryController.cs` to adjust method signatures for `GetReferenceTypes` and `GetEnvelopeStatus`, allowing optional parameters for better conditional responses. Added necessary using directives.

EnvelopeGenerator.Extensions/MemoryCacheExtensions.cs

@@ -1,4 +1,5 @@
 using Microsoft.Extensions.Caching.Memory;
+using System;
 
 namespace EnvelopeGenerator.Extensions;
 
@@ -7,15 +8,13 @@ public static class MemoryCacheExtensions
     public static IDictionary<string, int> GetEnumAsDictionary<TEnum>(this IMemoryCache memoryCache)
         where TEnum : Enum
     {
-        var referenceTypes = Enum.GetValues(typeof(TEnum))
-                                 .Cast<TEnum>()
-                                 .ToDictionary(rt =>
-                                 {
-                                     var key = rt.ToString();
-                                     var keyAsCamelCase = char.ToLowerInvariant(key[0]) + key[1..];
-                                     return keyAsCamelCase;
-                                 }, rt => Convert.ToInt32(rt));
+        var dict = new Dictionary<string, int>();
 
-        return referenceTypes;
+        foreach (TEnum role in Enum.GetValues(typeof(TEnum)))
+        {
+            dict[role.ToString()] = Convert.ToInt32(role);
+        }
+
+        return dict;
     }
 }