Add dnd-character

[BNAndras]

For #48in24. I defined helper functions the test suite can invoke to test the code as intended in the problem specs. I left the immutable test in to guide the students towards objects. I bumped up the difficulty as a result.

[loziniak]

I totally don't understand how test-character-abilities function can test if each ability is only calculated once...

[BNAndras]

While back, there apparently was a student that had a solution where the getter was not in fact a getter but instead calculated the ability score each time it was called. So the test makes sure the score doesn’t change when the getter is used. For our purposes, that test can be skipped I think.

[kotp]

I totally don't understand how test-character-abilities function can test if each ability is only calculated once...

It is likely not a bullet proof test, (I have not looked at this version of that test with the "bulletproof" criteria), but when it changes, this should pick it up, at least occasionally.

Do you want to have it exist and see how it is received by the students? That is my predisposition for something like that.