create courses

[mikeoleynik]

General

The mentor must be able to create a course and add theme to it. The course looks like a theme's list contains inside tasks.

User stories

• Mentor can create course;
• Mentor can add task to course;
• Task open consistently;
• Theme can exist separately or belongs to courses;
• All tasks of theme enter the course.
• When completing all tasks of theme (one course), opens access to the next theme.
• Access to the next task gives the teacher

Backend:

• model Course, field: :title
• model Theme, add field: :course_id (optional: true)

Issue: #4 Create course