Change no-op methods in Shield::Hash to abstract defs

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased] - 
+
+### Changed
+- Change no-op methods in `Shield::Hash` to `abstract def`s
+
 ## [1.2.0] - 2024-07-05
 
 ### Fixed

src/shield/utilities/mixins/hash.cr

@@ -1,9 +1,4 @@
 module Shield::Hash
-  macro included
-    def hash : String
-    end
-
-    def verify?(digest : String) : Bool
-    end
-  end
+  abstract def hash : String
+  abstract def verify?(digest : String) : Bool
 end