Proposal: generate `codelists.txt` file from selected codelists

Background
For studies in OpenSAFELY it is almost always necessary to create a codelists.txt file which lists each codelist required from OpenCodelists, including the organisation/user name and version number. Example:

Proposal
Rather than copying and pasting each codelist manually into the file, it would be helpful if users could create this file in OpenCodelists. E.g.

• select a variety of codelists in OpenCodelists (e.g. through checkboxes or an "add to basket" button on each codelist page),
• add them to a list/collection (akin to a shopping basket)
• review the basket (the codelists should ideally be clickable links, and ideally show whether the latest version of each codelist is selected or not).
• edit the basket (e.g. remove items)
• save the basket for later
• export the basket as a ready-made codelists.txt file (or part thereof, from which text could be copied into an existing file e.g. from a similar study)

Questions

• Do others think this would be useful?
• Can users have more than one basket at one time (e.g. for two studies)?
• Can users share baskets?
• It may also be useful if other information can (optionally?) be viewed/downloaded, such as the coding system, which is required for each codelist to be used in a study, normally specified in a codelists.py file. Example:
  

No files, tests, or entry points are named. Start by reviewing the existing codelist selection and export flows, then clarify whether baskets, version handling, sharing, and coding-system output are in scope. Done should include an agreed design and an implemented way to save, edit, and export selected codelists as codelists.txt.