Migrate from deprecated SharedPreferences to SharedPreferencesAsync #1276
Description
A mixture of using the outdated SharedPreferences (like currently in this package) and SharedPreferencesAsync in the users code causes issues. For example, any call to SharedPreferencesAsync will overwrite values of SharedPreferences even for other keys. This causes the access and refresh token to be outdated/wrong.
A solution is to migrate to the new SharedPreferencesAsync. This requires the user to migrate to the new classes as well, but that's planned by the shared_preferences plugin anyway. This would require explicit documentation in the migration notes for existing users, but also for new users starting with v3.
There is already an open pr for this: #1164
Links:
https://pub.dev/packages/shared_preferences#migration-and-prefixes