fix/pdf group and group technician

[Herafia]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !45124
• When generating a PDF, the group and the technician group were identical.
  groups_id and groups_id_tech are now arrays (AssignableItem type), rather than integers. A helper function, getGroupDisplayName(), has been added to handle both formats for compatibility.

Screenshots (if appropriate):