Modularize API token management in GRAPPA drivers

[ishank011]

https://github.com/cs3org/reva/tree/master/pkg/cbox/group/rest and https://github.com/cs3org/reva/tree/master/pkg/cbox/user/rest have a lot of overlapping code which can be reused.

[jimil749]

Hi @ishank011! I would like to work on this, if that's fine. So I suppose, we are to move out duplicated methods out of user/rest.go and group/rest.go into a separate file to prevent duplication?

[ishank011]

Hi @jimil749! Yep, that's precisely it. cbox has a utils package so you can move these there or create a separate one.

[jimil749]

@ishank011 I had a question. Since we have the manager struct and its methods repeated in the user and group package, do I need to move the entire manager struct (which will then implement both user.Manager and group.Manager interface) and its methods into the utils package and then call those methods from the respective packages i.e user/rest and group/rest?

[ishank011]

Having the same struct implement both the interfaces won't be a good idea as the interface methods are totally different. Let's keep them separate.