#12 - grade columns and grade crud

[kamilpiech97]

This should close #12.
Added CRUD for managing grade columns in student group and adding grades for students.
Added some tests.

Preview:

Screencast.from.22-10-23.11.08.16.webm

[EwelinaSkrzypacz]

1. If we're checking for presence, it should remain as it currently is. But once the cell has a state (presence), any state changes should be triggered by a double click. Why? Because now we can't write negative assessment on red background.

2. When I write too long string on grades, I see error:

3. We should change delete column icon from trash to x mark, because we have x mark icon in whole application.

[EwelinaSkrzypacz]

Suggested change

	{{ student.index_number }} ({{ student.first_name }} {{ student.surname }} )
	{{ student.index_number }} ({{ student.first_name }} {{ student.surname }})

[EwelinaSkrzypacz]

1. I believe that the width of the columns should be fairly consistent. Alternatively, should we consider adjusting it based on the length of the contained text?

2. Please fix warnings from dev console

[EwelinaSkrzypacz]

1. Icons is too small - maybe instead of arrows we should make draggable columns>

2. What a shame that we have to scroll the table, maybe we can do this something with it?

[EwelinaSkrzypacz]

This is a nitpicking a bit, but I think I will change some colors:

• instead of bg-green-300 please set bg-lime-200
• change bg-red-300 to bg-rose-300
• set text color to text-grey-900