docker/keycloak: Enable users registration
For testing purposes allow to register new users in Keycloak database by enabling the Register link in login page.
To match production settings, email verification is also enabled. Emails are sent by a MailHog instance, a fake STMP server for testing environments. All mails sent by Keycloak can be read from a Web UI located at http://localhost:8025/.
Migrated from D5882 (view on Phabricator)