Add checks for profanity to profile updates (#12445)

* fix(profile): detect attempt to use banned words as display name. refactor profanity detection method.

* fix(profile): detect attempt to use banned words in blurb. further refactor profanity detection. inform the user their chat privileges have been revoked.

* refactor: add function to normalize Unicode strings and remove diacritics

* fix: improve regEx to prevent false partial matches e.g. 'hello' being recognised as banned words. porting fix from #12309

* fix(profile): refactor of profanity detection for #12445

* fix(profile): add test for swear words in new profile. fix existing tests

* fix(profile): show different error message for attempted slur use in username by new users.

* fix(profile): remove incorrect slur test

* fix(profile): fix slurs not caught at start of end of strings connect by punctuation

* tests(profile): fix tests for profanity checking

* remove exclusive test

* 11865 - update text for slur warnings

* 11865 - remove unused string from locale files

* 11865 - improve naming of banned word usage locale string

* 11865 - improve logic so that differentiated warnings are shown depending on whether a slur or other profanity has been used in a display name

* 11865 - construct slur regexes outside the validation function in which they are used

* 11865 - fix tests

test/api/v4/user/auth/POST-user_verify_username.test.js

@@ -51,9 +51,6 @@ describe('POST /user/auth/verify-username', async () => {
       await expect(user.post(ENDPOINT, {
         username: 'something_TESTPLACEHOLDERSLURWORDHERE',
       })).to.eventually.eql({ isUsable: false, issues: [t('usernameIssueLength'), t('usernameIssueSlur')] });
-      await expect(user.post(ENDPOINT, {
-        username: 'somethingTESTPLACEHOLDERSLURWORDHEREotherword',
-      })).to.eventually.eql({ isUsable: false, issues: [t('usernameIssueLength'), t('usernameIssueSlur')] });
     });
 
     it('errors if username is not allowed', async () => {