Add association habtm between user and lesson to keep track of course progress
Create join table between user and lesson
Add resource for action completed
Add action completed responsible_for marking lesson as finished or not
Add methods to checking that lesson is completed or not. Add methods responsible for marking lesson(add or delete user from list)
Add method that checking what progress user made through course. Return result in percent as string
Add progress bar for course
Label on button depends on lesson completion
Label on button depends on lesson completion
Setup factory for lesson
Add tests for lesson completion
Add test to checking course progress