xmd download with Field name longer than 40 characters

Hello,

I've got an error whil downloading xmd json from dataset with fields name longer than 40.
Normally we can have field name > 40 char even it's not really recommended.

field name {XXXX} is greater than 40 characters

Thanks!

Reproduce the xmd JSON download using a dataset containing a field name longer than 40 characters and capture the reported error. Trace the download entry point and validation that rejects the field name. Done means the download completes successfully while preserving the long field name.

Written by the indexing model from the issue text.