Provide a way to iterate through json arrays/objects

Currently the approach to iterate over a json array is to

string(JSON LENGTH)
math(length-1)
foreach(index RANGE length-1)
string(JSON GET "index")
...
endforeach()

which is terribly inefficient since string(JSON) inside the foreach() has to reparse the whole json again over and over.

Would it be possible to have a

foreach(json_elem IN JSON json_var)

which is capable to iterate over each object/index?

I would also advocate for providing a cmake variable string(JSON) API instead of the string based one since the current approach clutters --trace-exapnd output a lot.