Make user provide only learning material's title and content

[Iamhexi]

Background

A reviewer suggested:

Also, I would say, the user should have no say in the topic where file should be stored, they only provide material title and other required stuff, and the backend data is being autogenerated.

Goal

The goal of the the task is to make path independent of user's choice. User should only provide a title and material's content. Path should be auto-generated and deterministic given its content. ID cannot be used for now as it is generated automatically, however, this implementation details may change.

[Iamhexi]

Solved by #20 and it has been merged, closing.