Potential issue

[ahasverus]

When using the function td_create_metadata_file(), we check if the file with the same extension (.yml or .xlsx) exists.

But is it a good idea to allow user having the two formats for the same database? This can create conflicts if he/she edits the .yml and later edits the .xlsx. Maybe we should consider keeping one single format but allowing user to convert the file into another format (with td_read_metadata_file("yml") and td_save_metadata_file("xlsx")).