Support pkce in the oidc login provider

[Andreas-Hjortland]

Hi, I was wondering if you are positive to adding support for PKCE in the OAuth provider as OAuth version 2.1 requires pkce^[1] for all authorization_code clients. At the moment most providers don't require it, but one I wanted to try to use with Rallly does.

If I understood it correctly, the only thing we have to do is to add the "pkce" string to the "checks" array in the OIDC provider. I can create a pull request for it if you want :)

[lukevella]

@Andreas-Hjortland, thanks for bringing this up. I'll include this in the next self-hosted release. See #1678

[ThisIsMissEm]

FYI, this has landed (I'm looking through the discussions and happened to notice this wasn't resolved)