Watch the `htpasswd` file for changes and update the `htpasswdMap` (#1701)

* dynamically update the htpasswdMap based on the changes made to the htpasswd file

* added tests to validate that htpasswdMap is updated after the htpasswd file is changed

* refactored `htpasswd` and `watcher` to lower cognitive complexity

* returned errors and refactored tests

* added `CHANGELOG.md` entry for #1701 and fixed the codeclimate issue

* Apply suggestions from code review

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Fix lint issue from code suggestion

* Wrap htpasswd load and watch errors with context

* add the htpasswd wrapped error context to the test

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>