Use multiple columns concatenation to generate an id

Problem/Motivation

Sometimes, what can uniquely identify an entry is stored on multiple columns. Being able to generate an entry ID using multiple columns can be required to discriminate them.

Proposed resolution

Add an optional form field to enter a list of columns to concatenate to generate an ID. We could start with a simple syntax like 1+2+3 to concatenate the 3 first columns (or use their name instead of their numeric values).

Remaining tasks

Implementation.

User interface changes

A new option.