Add option to not consider word boundaries when processing keyword filtering (#7975)

* Add option to not consider word boundaries when filtering phrases

* Add a few tests for keyword/phrase filtering

app/serializers/rest/filter_serializer.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
 class REST::FilterSerializer < ActiveModel::Serializer
-  attributes :id, :phrase, :context, :expires_at,
+  attributes :id, :phrase, :context, :whole_word, :expires_at,
              :irreversible
 end