Add config option for disabling email MX check

[skgsergio]

This PR adds the option for disabling the MX check over the user email when a user tries to register.

This is required in some environments without Internet connectivity.

[gonzaloriestra]

👌

[skgsergio]

How to CR

Since in staging we check the mail also in central the best way to check this is working is the following:

$ RAILS_ENV=staging BUILDER_ENABLED=true SUBDOMAIN=thisshouldwork PASSWORD=thisshouldwork12345 EMAIL=sconde+test@carto.com bundle exec rake cartodb:db:setup_user
User thisshouldwork created successfully

$ RAILS_ENV=staging BUILDER_ENABLED=true SUBDOMAIN=patatasfritas PASSWORD=patatasfritas12345 EMAIL=test@carto.lan bundle exec rake cartodb:db:setup_user
rake aborted!
{:email=>["Domain name not registered"]}

Tasks: TOP => cartodb:db:setup_user
(See full trace by running task with --trace)

Then add disable_email_mx_check: false to the config and restart both unicorn and resque and test again, you should get the same results:

$ RAILS_ENV=staging BUILDER_ENABLED=true SUBDOMAIN=thisshouldwork2 PASSWORD=thisshouldwork12345 EMAIL=sconde+test2@carto.com bundle exec rake cartodb:db:setup_user
User thisshouldwork2 created successfully

$ RAILS_ENV=staging BUILDER_ENABLED=true SUBDOMAIN=patatasfritas PASSWORD=patatasfritas12345 EMAIL=test@carto.lan bundle exec rake cartodb:db:setup_user
rake aborted!
{:email=>["Domain name not registered"]}

Tasks: TOP => cartodb:db:setup_user
(See full trace by running task with --trace)

And then change it to disable_email_mx_check: true:

$ RAILS_ENV=staging BUILDER_ENABLED=true SUBDOMAIN=thisshouldwork3 PASSWORD=thisshouldwork12345 EMAIL=sconde+test3@carto.com bundle exec rake cartodb:db:setup_user
User thisshouldwork3 created successfully

$ RAILS_ENV=staging BUILDER_ENABLED=true SUBDOMAIN=patatasfritas PASSWORD=patatasfritas12345 EMAIL=test@carto.lan bundle exec rake cartodb:db:setup_user
User patatasfritas created successfully

[gonzaloriestra]

✔️ Acceptance OK

@skgsergio sorry for the delay 🙈

[gonzaloriestra]

retest this please

[gonzaloriestra]

retest this please

[gonzaloriestra]

retest this please

[gonzaloriestra]

retest this please