Address review comments.

app/models/concerns/atomic_internal_id.rb

@@ -24,24 +24,21 @@
 module AtomicInternalId
   extend ActiveSupport::Concern
 
-  included do
-    class << self
-      def has_internal_id(on, scope:, usage: nil, init:) # rubocop:disable Naming/PredicateName
-        before_validation(on: :create) do
-          if self.public_send(on).blank? # rubocop:disable GitlabSecurity/PublicSend
-
-            scope_attrs = [scope].flatten.compact.each_with_object({}) do |e, h|
-              h[e] = self.public_send(e) # rubocop:disable GitlabSecurity/PublicSend
-            end
-
-            usage = (usage || self.class.name.tableize).to_sym
-            new_iid = InternalId.generate_next(self, scope_attrs, usage, init)
-            self.public_send("#{on}=", new_iid) # rubocop:disable GitlabSecurity/PublicSend
+  module ClassMethods
+    def has_internal_id(on, scope:, usage: nil, init:) # rubocop:disable Naming/PredicateName
+      before_validation(on: :create) do
+        if self.public_send(on).blank? # rubocop:disable GitlabSecurity/PublicSend
+          scope_attrs = [scope].flatten.compact.each_with_object({}) do |e, h|
+            h[e] = self.public_send(e) # rubocop:disable GitlabSecurity/PublicSend
           end
-        end
 
-        validates on, presence: true, numericality: true
+          usage = (usage || self.class.table_name).to_sym
+          new_iid = InternalId.generate_next(self, scope_attrs, usage, init)
+          self.public_send("#{on}=", new_iid) # rubocop:disable GitlabSecurity/PublicSend
+        end
       end
+
+      validates on, presence: true, numericality: true
     end
   end
 

app/models/internal_id.rb

@@ -67,16 +67,17 @@ class InternalId < ActiveRecord::Base
     # usage: Symbol to define the usage of the internal id, see InternalId.usages
     # init: Block that gets called to initialize InternalId record if not present
     attr_reader :subject, :scope, :init, :scope_attrs, :usage
+
     def initialize(subject, scope, usage, init)
       @subject = subject
       @scope = scope
       @init = init
       @usage = usage
 
-      raise 'scope is not well-defined, need at least one column for scope (given: 0)' if scope.empty?
+      raise ArgumentError, 'scope is not well-defined, need at least one column for scope (given: 0)' if scope.empty?
 
       unless InternalId.usages.keys.include?(usage.to_s)
-        raise "Usage '#{usage}' is unknown. Supported values are #{InternalId.usages.keys} from InternalId.usages"
+        raise ArgumentError, "Usage '#{usage}' is unknown. Supported values are #{InternalId.usages.keys} from InternalId.usages"
       end
     end