The recipe link is very important, for example so I can click through and return the system (since there is no return2beaker.sh). The body of the mail even advises doing exactly that, but doesn't provide a link for it.
I (unwittingly) fixed this bug in this commit:
which will be in 19.0.
Steps to reproduce:
1. Schedule a job like this:
2. Wait for installation to complete and reservation e-mail to be sent
Reservation e-mail contains a link to the recipe in Beaker's web UI.
Beaker 19.0 has been released.