[Easy pick] All final classes must have an interface about oauth2-bundle

[X-Coder264]

I think everything here that was mentioned is solved. Feel free to open a new issue if there are still things that need to be improved.

[X-Coder264]

I don't think we should blindly add interfaces to all final classes in the bundle just for some "test" purposes. For example I don't see any value in adding an interface for the UserConverter class. I don't see the possibility of there being another implementation that justifies an interface (or it's very unlikely at least) nor does this implementation do any I/O or database calls etc which means doing new UserConverter() in your tests is fine if you ask me.

[Nyholm]

No, not "blindly". Final classes that are not "internal" should have an interface.

Speaking of your example of UserConverter:
I like the OauthAuthorizationController but I need do to some modifications to it. So I copied that class to my namespace and did my modifications. (Everything is perfect.) However, when I write unit tests from my new controller class I cannot mock its dependencies. That is reason 1 why we need an interface.

Reason 2 is that OauthAuthorizationController has dependency on a concrete class. That violates the dependency inversion principle.

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You are probably correct when you say that there will most likely not be an other implementation of the UserConverter. However, adding an interface to be more correct will guarantee future proof code.

[alexspark21]

Yep, I think we have to set UserConverterInterface, because I have to have possibility override UserConverter and implement my logic

[janvernieuwe]

I just ran into a situation where a ScopeInterface would have been nice.
When retrieving scopes from a custom system you could just implement it and return them.