Refactor RestType enum: remove Invalid, use byte

RestType now inherits from byte for efficiency. The Invalid value has been removed from the enum, and the IsValid extension method was updated to reflect this change by only checking for None.

src/ReC.Domain/Constants/RestType.cs

@@ -1,6 +1,6 @@
 namespace ReC.Domain.Constants;
 
-public enum RestType
+public enum RestType : byte
 {
     None = 0,
     Get = 1,
@@ -12,7 +12,6 @@ public enum RestType
     Options = 7,
     Connect = 8,
     Trace = 9,
-    Invalid = -1,
 }
 
 public static class RestTypeExtensions
@@ -24,6 +23,6 @@ public static class RestTypeExtensions
 
     public static bool IsValid(this RestType restType)
     {
-        return restType != RestType.Invalid && restType != RestType.None;
+        return restType != RestType.None;
     }
 }