Merge branch 'pkoppenb-DecayTreeFitterAlg' into 'master'

DecayTreeFitterAlg to access refitted candidates

See merge request !970
2 jobs for master in 32 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Test
passed check-copyright #17820285

00:00:32

passed check-formatting #17820286

00:00:23