* [FEATURE][BREAKING] Allow users to sign in with email.
The users_filter purpose evolved with the introduction of username_attribute
but is reverted here to allow the most flexibility. users_filter is now the
actual filter used for searching the user and not a sub-filter based on the
username_attribute anymore.
* {input} placeholder has been introduced to later deprecate {0} which has been
kept for backward compatibility.
* {username_attribute} and {mail_attribute} are new placeholders used to back
reference other configuration options.
Fix#735
* [MISC] Introduce new placeholders for groups_filter too.
* [MISC] Update BREAKING.md to mention the change regarding users_filter.
* [MISC] Fix unit and integration tests.
* Log an error message in console when U2F is not supported.
* Apply suggestions from code review
* Update BREAKING.md
Co-authored-by: James Elliott <james-d-elliott@users.noreply.github.com>
Co-authored-by: Amir Zarrinkafsh <nightah@me.com>
