introduce oidc middleware

[butonic]

based on https://github.com/cs3org/reva/tree/master/pkg/auth/manager/oidc

It needs quite a bit of configuration. Will sort that out while testing with @DeepDiver1975

[tboerger]

If you are using the same options pattern we are using already everywhere within the ocis repos you can define defaults much cleaner.

[butonic]

ok, so I move the options to individual functions inside pkg/ocis/options.go and implement a newOptions(o Option...) that fills the options object that is private to the middleware. right? at least somewhat?

[butonic]

@tboerger currently the middlewares all take explicit arguments ... that would be quite a list in this case ... I'd prefer to have a func OpenIDConnect(opts ...Option) func(http.Handler) http.Handler { signature than 9 parameters

[butonic]

ok. @tboerger Does this make sense? I am asking because all other middlewares take explicit parameters ...

[tboerger]

func OpenIDConnect(opts ...Option) func(http.Handler) http.Handler { is what I was refering to. That's the scheme we are using for all the ocis repos.

[butonic]

but for middlewares like Static we have func Static(root string, fs http.FileSystem) func(http.Handler) http.Handler {. They don't follow that pattern because ... it's only two parameters? When do we start using the options pattern ... if that is a thing ... 3 parameters? 4? when the number starts to suck?

Just trying to find something we can note down as a coding guideline ... somewhere...

[tboerger]

Indeed I have not done that for these 2 cases of the middlewares because there are only 2 options. Feel free to add options for all of them to keep it consistent with the other repos.