send welcome email as soon as possible after freebie invoicing
call send_welcome_email w flag denoting log user back in
add login_with_key capability to trialists with subscription; set the activation key manually; call create_guest_user with do not login flag
use a go-slog call rather than aborting the subscribe_free_period entirely, if sync fails
code review: add comment
Merge pull request #37 from okredo/issues-4541-no-welcome-email

send welcome email as soon as possible after freebie invoicing