Merge branch 'feature/ci-lecture-branch-as-variable' into 'master'

[ci] Make triggered dumux-lecture branch a variable

See merge request !2819

(cherry picked from commit c0aa0c60)

890f79c7 [ci] Make triggered dumux-lecture branch a variable
5 jobs for !2820 with cherry-pick-c0aa0c60
latest detached
Status Name Job ID Coverage
  Trigger
manual full-dune-2.7-clang
manual full-dune-2.7-gcc
manual full-dune-master-gcc
manual minimal-dune-2.7-gcc
 
  Downstream Modules
created trigger lecture