FIX: Add word boundaries to replace and tag watched words (#13405)

The generated regular expressions did not contain \b which matched
every text that contained the word, even if it was only a substring of
a word.

For example, if "art" was a watched word a post containing word
"artist" matched.

spec/components/post_creator_spec.rb

@@ -502,13 +502,21 @@ describe PostCreator do
             end
 
             context "without regular expressions" do
-              it "works" do
+              it "works with many tags" do
                 Fabricate(:watched_word, action: WatchedWord.actions[:tag], word: "HELLO", replacement: "greetings , hey")
 
                 @post = creator.create
                 expect(@post.topic.tags.map(&:name)).to match_array(['greetings', 'hey'])
               end
 
+              it "works with overlapping words" do
+                Fabricate(:watched_word, action: WatchedWord.actions[:tag], word: "art", replacement: "about-art")
+                Fabricate(:watched_word, action: WatchedWord.actions[:tag], word: "artist*", replacement: "about-artists")
+
+                post = PostCreator.new(user, title: "hello world topic", raw: "this is topic abour artists", archetype_id: 1).create
+                expect(post.topic.tags.map(&:name)).to match_array(['about-artists'])
+              end
+
               it "does not treat as regular expressions" do
                 Fabricate(:watched_word, action: WatchedWord.actions[:tag], word: "he(llo|y)", replacement: "greetings , hey")
 

spec/components/pretty_text_spec.rb

@@ -1420,6 +1420,10 @@ HTML
       expect(PrettyText.cook("Lorem ipsum dolor sittt amet")).to match_html(<<~HTML)
         <p>Lorem ipsum something else amet</p>
       HTML
+
+      expect(PrettyText.cook("Lorem ipsum xdolor sit amet")).to match_html(<<~HTML)
+        <p>Lorem ipsum xdolor sit amet</p>
+      HTML
     end
 
     it "replaces words with links" do