Support for fonts with custom glyph names

[Beatris]

I'm dealing with a pdf document with font that has some custom glyph names (i.e. glyph names not in AGL and do not follow AGLFN).
As a result, I get "(cid:)" in the parsed text.

To overcome this I'll have to change the cid2unicode map of the font. It would be very helpful to be able to configure the pdfminer to load this map from a separate font file. So, it can accept a folder where there will be some font files and will load the cid2unicode from there (if such file exists) using a tool like https://fonttools.readthedocs.io/en/latest/#

[JKsang]

Can you give an example how to configure the pdfminer to load this map from a separate font file ?