Previously, only the direct children of a recurrent tasks were copied
during a recurrence. Also, the child tasks which had a recurrence were
copied with the recurrence_id of the initial subtask, which lead the new
subtask to be linked with the recurrence of the initial subtask.
With this commit we copy the children until the 3rd layer. Also,
we hard copy the recurrence of the initial subtask and link this new
recurrence with the new subtask, to make it decoupled from the initial
subtask recurrence. Furthermore, if several initial subtasks has been
created with a same recurrence, only the first subtask is copied.
PR: #77126
task-2522076
X-original-commit: 808a965b4171a386f3987071c19cc27783ba0119
Thibault Libioulle
987023f3b5