DEV: enable frozen string literal on all files

This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.

Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging

lib/freedom_patches/safe_buffer.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # For some reason safe buffer is getting invalid encoding in some cases
 # we work around the issue and log the problems
 #
@@ -15,9 +17,9 @@ class ActiveSupport::SafeBuffer
       raise
     else
 
-      encoding_diags = "internal encoding #{Encoding.default_internal}, external encoding #{Encoding.default_external}"
+      encoding_diags = +"internal encoding #{Encoding.default_internal}, external encoding #{Encoding.default_external}"
 
-      unless encoding == Encoding::UTF_8
+      if encoding != Encoding::UTF_8
         encoding_diags << " my encoding is #{encoding} "
 
         self.force_encoding("UTF-8")
@@ -28,7 +30,7 @@ class ActiveSupport::SafeBuffer
         Rails.logger.warn("Encountered a non UTF-8 string in SafeBuffer - #{self} - #{encoding_diags}")
       end
 
-      unless value.encoding == Encoding::UTF_8
+      if value.encoding != Encoding::UTF_8
 
         encoding_diags << " attempted to append encoding  #{value.encoding} "