LearnDash course access

Use this when a plugin, theme, migration, checkout bridge, import, or custom frontend needs to decide whether a user can access a LearnDash course or must grant/revoke direct course enrollment.

Do not reduce LearnDash access to one usermeta key. In LearnDash 5.1.9, course access can come from direct enrollment, group enrollment, open courses, sample steps, admin auto-enroll, free/paynow settings, start/end dates, expiration rules, and legacy access-list mode.