Jenkins notifications doesn't cut our needs

Originally created by @intrigeri on #9660 (Redmine)

We discovered two issues with the Mailer plugin:

https://jenkins.tails.boum.org/job/build_Tails_ISO_bugfix-8007-AppArmor-hardening/48/console says An attempt to send an e-mail to empty list of recipients, ignored. and indeed, no emails are sent.

=> The send-to-individuals setting do not notify on scheduled builds as no scm changes happened.

https://jenkins.tails.boum.org/job/build_Tails_ISO_bugfix-8007-AppArmor-hardening/49/console sent an email to all the last committers since the last build.

Parent Task: tails/sysadmin#6196

Related issues

• Related to tails/sysadmin#6216