Tests for AffineSchemes

[simonbrandhorst]

And some bugfixes.

[afkafkafk13]

Please take care of the two minor comments.

Just curiosity: Concerning the tests, how much of the functionality of AffineSchemes.jl is now covered by tests (approximately)?

[thofma]

https://app.codecov.io/gh/oscar-system/Oscar.jl/blob/master/experimental/Schemes/AffineSchemes.jl

63% (before this PR)

Once the tests pass, there will be a codecove/patch item showing up in the lists of checks below. Then one can inspect how the coverage changed.

[fingolfin]

Once (if) tests pass, one also gets inline comments like this in the "Files" tab that indicates which lines modified by the PR are not covered. That can be useful: submit your code as a (draft) PR, see which parts are under tested, add tests, repeat.

[simonbrandhorst]

Thank you for your comments. I set to auto merge. Once there is a single positive review.