Make another volume with exercises [.noedit & Last-modified through api]

[Nircek]

What do you think about running a script that fetches new updates from the Pikne-Programy/pikne-zadania-exercises repo?
Currently, we need to update the submodule, commit it, and wait for a build. That would be troublesome in the future.

[Nircek]

We can use this: https://github.com/opsxcq/tasker

[Nircek]

Or maybe, it will be better to make the volume with exercises and optionally update it with the other container?

[Nircek]

I think the automatic updates are not possible in case we want to give users a possibility to change existing exercises. It would be just too complicated process and should be made manually (it will not be just git pull).

[Nircek]

It would be nice to have a possibility to lock the exercise volume during an update. Creating a file .noedit will prevent the server from changing files.

[Nircek]

The volume works. I added it in f0a4a56. I keep the issue open to remind me of .noedit file.

[Nircek]

When an admin creates a .noedit file, we can expect they made some changes on the disk, so it would be nice to reload the exercises (if we don't sync it with disk events #41).

Nevertheless, a user can make a change simultaneously. I assume we should store a timestamp of the last fetch from the database and then, the server can compare it with the stored one. When the requested change has an older timestamp, it indicates the server should abort that request because it would overwrite the admin's changes.

@miloszwasacz, what do you think about this that? Feel free to edit the API docs when you figure something out.

[Nircek]

Okay, the primary issue is resolved and IMO the .noedit and Last-modified would be good only in case of getting #41 true. Closing...