Support scope as an array

[balazsorban44]

Thank you for this awesome library!

Currently, the scope in AuthorizatinoParameters can only be of type string.
https://github.com/panva/node-openid-client/blob/772306cc82b72ace9361f4a945249a5c35a8f921/types/index.d.ts#L138

This is merely a suggestion, but since the claims property has also special handling, I was wondering if we could make an exception for scope as well since it is an often-used parameter.

Related: nextauthjs/next-auth#2511 (comment)

I am happy to open a PR implementing this if the author approves of the idea!

Relevant code is probably here:

https://github.com/panva/node-openid-client/blob/772306cc82b72ace9361f4a945249a5c35a8f921/lib/client.js#L84-L86

I have seen scopes being sent with separators like , +, ,. node-oauth uses querystring.stringify():
https://github.com/ciaranj/node-oauth/blob/a7f8a1e21c362eb4ed2039431fb9ac2ae749f26a/lib/oauth2.js#L174
, which produces something like this: ?scope=openid&scope=email

new URLSearchParams({scope: ["openid", "email"]}) produces ,.

Is there any consequence to choose any concatenating over the other? Is this something that can be interpreted differently from Provider to Provider and so that is the reason scope as an array isn't supported?

[panva]

Feel free to propose a PR, the only correct way is to .join() the array with a space ' ' as the separator. Everything else is just plain wrong ;)

• scope=openid&scope=email - wrong because it submits duplicate parameters and rejected by a conform AS
• scope=openid,email - wrong because it is parsed as a single scope value by a conform AS

[balazsorban44]

Thank you! Will have a look then!