feat: move PD Core into Essentials

src/PepperDash.Core/XSigUtility/Tokens/XSigToken.cs

@@ -0,0 +1,45 @@
+namespace PepperDash.Core.Intersystem.Tokens
+{
+    /// <summary>
+    /// Represents the base class for all XSig datatypes.
+    /// </summary>
+    public abstract class XSigToken
+    {
+        private readonly int _index;
+
+        /// <summary>
+        /// Constructs an XSigToken with the specified index.
+        /// </summary>
+        /// <param name="index">Index for the data.</param>
+        protected XSigToken(int index)
+        {
+            _index = index;
+        }
+
+        /// <summary>
+        /// XSig 1-based index.
+        /// </summary>
+        public int Index
+        {
+            get { return _index; }
+        }
+
+        /// <summary>
+        /// XSigToken type.
+        /// </summary>
+        public abstract XSigTokenType TokenType { get; }
+
+        /// <summary>
+        /// Generates the XSig bytes for the corresponding token.
+        /// </summary>
+        /// <returns>XSig byte array.</returns>
+        public abstract byte[] GetBytes();
+
+        /// <summary>
+        /// Returns a new token if necessary with an updated index based on the specified offset.
+        /// </summary>
+        /// <param name="offset">Offset to adjust the index with.</param>
+        /// <returns>XSigToken</returns>
+        public abstract XSigToken GetTokenWithOffset(int offset);
+    }
+}