Enable frozen string literals.

Make all string literals immutable by default.

app/logical/concerns/array_attribute.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ArrayAttribute
   extend ActiveSupport::Concern
 

app/logical/concerns/deletable.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # A concern that adds common helper methods to models that are soft deletable.
 #
 # @example

app/logical/concerns/has_bit_flags.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module HasBitFlags
   extend ActiveSupport::Concern
 

app/logical/concerns/mentionable.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # A concern that handles @mentions in comments and forum posts. Sends a DMail
 # to mentioned users when a comment or forum post is created or edited to add
 # new mentions.

app/logical/concerns/normalizable.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Normalizable
   extend ActiveSupport::Concern
 

app/logical/concerns/searchable.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Searchable
   extend ActiveSupport::Concern