Update help text for COM and TITLE parameters

[sergei-maertens]

Thema / Theme

Admin

Omschrijving / Description

The available variable public_reference is documented, but it would be better to document this as {{ public_reference }} to make the template syntax clear, since the general configuration uses a different format (single curly braces).

Added value / Toegevoegde waarde

Reduce confusion

Aanvullende opmerkingen / Additional context

Direct .format calls/syntax should be avoided, so the general configuration is "wrong" here - instead this should be passed through the sandbox template engine, but that would be a breaking change.

[joeribekker]

Refinement: Replace public_reference with {{ public_reference }} in model help_text and/or readthedocs. If its more/harder than this, let me know.