Hi,

[my current version: 2022.05.02 16:19]
With the past two-or-so uploads, btx output seems to be broken in some cases. 
Compiling the below example

  \usebtxdataset[refs.bib]
  \usebtxdefinitions[aps]

  \starttext
  This reference has a tag which is in camel-case:
  \cite[Nielsen2011_ChernoffInformationExponentialFamilies]

  On the other hand this reference has a tag which is lower-case:
  \cite[vaart1998_asymptoticstatistics]

  \placelistofpublications
  \stoptext

along with the bibtex file (refs.bib attached here), only the second citation 
entry has a properly rendered bibliography entry while the first one does not. 
Notably, any bibtex entries whose tags are not all lowercase (ASCII) are not 
rendered correctly. Instead, in the log I get

publications > unknown tag 'nielsen2011_chernoffinformationexponentialfamilies' 
in dataset 'default'

Almost all my entries in bib files are in camel-case since I find that to be 
easier to read and it gives me a better clue of what the item is. With some 
recent uploads I noticed that in publ-ini.lua 'tag' and 'field' entries were 
string.lowered(). Upon removing those statements, I am able to get the proper 
output.

I also have certain bib files where the entries are not at all in ASCII (so I 
am not sure what the code might do there, I did not check in detail). I hope I 
can continue to use camel case for the tags (if its not too much to ask): is 
there some additional setting that I should change to allow this so that the 
output is rendered correctly?

Thanks,
  Sreeram