I’ve an older drupal 8 site in 8.5.x version. There are too many custom & contrib modules, eg acquia/blt, lightening, etc.
We need to update the site to latest, modules, core, etc. It uses composer 1.
What is the ideal way to approach the upgrade?
Should I directly try composer 2 and require drupal 9?
or should I update the codebase in batches? eg first update to 8.9.20 => Deploy it to dev/QA/production and then to 9.x?
or something else? Any helps would be appreaciated. I agree the custom modules, might need manual updates to code, eg core => core_version_requirement, etc.
It also uses jsonapi as a contrib module which i see is now merged to core drupal. Is it fine to simple composer remove drupal/jsonapi before update drupal/core? Should i be worried about its contents?