support linkIdentity

[johndpope]

as per supabase/auth#313

we need similar capabilities in swift / mobile

// assume user is already logged in and authenticated

// link the current user to a google identity
// this works very similar to signInWithOAuth() and will redirect the user to google to complete the oauth flow 
// once the oauth flow has been completed, the user will be redirected back to the app with the identity linked
const { data, error } = await supabase.auth.linkIdentity({ provider: 'google' })

// fetch all identities linked to the current user
const { data: { identities } } = await supabase.auth.getUserIdentities()

const googleIdentity = identities.find(identity => identity.provider === 'google')

// unlink an identity
await supabase.auth.unlinkIdentity(googleIdentity)

[grdsdev]

Hi @johndpope

Thanks for opening this issue, but it is a duplicate of #193

We're planning to add support for it in the next couple of weeks.

So I'll be closing this in favor of the other one.