feat(catalogue): ability to specify 'within-cell' separator in array cells in CSV export

[YpeZ]

Issue

Currently the CSV API joins the items of an array type in a cell with a comma, encapsulating terms that contain a comma with double quotation marks.
This makes it difficult for the user to unpack the values within these cells, especially when the field is an ontology array type containing a large number of values.
Consider the following 'psuedo-CSV' example where the terms within the cells are joined by a comma.

name	work days
A	Mon,Tue,Wed,Thu
B	Mon,Wed,Thu or Fri
C	Mon,Tue,"Wed, Thu or Fri"
D	"Tue, Wed or Fri",Mon,Thu

Note that the entries for persons C and D contain a term with a comma. This makes it difficult for programs parsing this input to distinguish between the comma that separates the values and the comma.

Solution

If the user were to be able to select a separator or specify a separator the situation above could be prevented.
Consider for example a small sequence of characters of which it can be assumed that it does not occur in the data itself and is 'safe' to use for other programs.

For example the separator ~~~ would enable a user parsing the export to separate the values again in their respective programming language

name	work days
A	Mon~~~Tue,Wed,Thu
B	Mon~~~Wed~~~Thu or Fri
C	Mon~~~Tue~~~"Wed, Thu or Fri"
D	"Tue, Wed or Fri"~~~Mon~~~Thu

Alternatives

No response

Additional context

Currently with Pyclient is not able to distinguish between the commas. The issue #4502 is related to this