Add generateLink method

[NiKoTron]

Added generateLink method reffer to the supabase's Auth(Server only) API

[bdlukaa]

I'm not sure we want to expose server APIs to this client library

@dshukertjr

[NiKoTron]

why not? For example, I use dart as a server language. Also there's api key based restriction to use this method, i guess it should be enough.

[dshukertjr]

@bdlukaa I was the one who said let's wait on implementing server side methods on these libraries, because I thought the js library was going to be separated into client side library and server side library on this issue, it hasn't been separated and I checked with the team, but it seems like we don't have immediate plans to separate it (still on the road map at some point though).

With Dart increasing in popularity as a server side language, perhaps we could reconsider it and start adding all the server side methods?

Related #26

[dshukertjr]

@NiKoTron Could we include a test as well for this amazing work that you have done?
https://github.com/supabase/gotrue-js/blob/master/test/GoTrueApi.test.ts#L294

[NiKoTron]

@dshukertjr Sorry for the late reply. I made tests similiar to JS impl. also added dart_jsonwebtoken as a dev_dependency to geneate service jwt.

[dshukertjr]

@NiKoTron Looks amazing! The momentum of server side dart community is amazing!