Well after testing, this is what I found:
When you try to use ANYELEMENT parameters, and even just a VARIADIC
TEXT[] parameter to support the optional delimiter argument:
FUNCTION GROUP_CONCAT_ATOM(ANYELEMENT, ANYELEMENT, VARIADIC
delimiters TEXT[])
when you go to create the aggregates, postgres runs through a
permutation of the argument types, just to be sure that all functions
are accounted for. And at that point postgres complains:
function group_concat_atom(text, anyelement, text) does not exist
You would _think_ that the function definition above would cover this
case, but it for whatever reason it does not.
In the process of trying variations, I see that I used the deficient
nomenclature of "field" instead of "column" in the previous code. I will
fix that and post at the other site listed above; but other than that,
the code works and I welcome anyone to come up with a more compact
version that allows it to remain as flexible as it is now...
