Change database encoding from utf8 to utf8mb4.

Course Units: Make a unit as a prerequisite.

Exercises: New question type “Fill in from predefined answers”.

User profile: Mark a course as `favorite` (favorite courses have a precedence in ordering).

H5p content. Course admin can export / import h5p content from one course to another.

Blog. Course admin can hide a blog post.

Assignments: Various improvements.

Questionnaires: Various improvements.

Δυνατότητα σύνδεσης με την υπηρεσία UserWay

Update jQuery library