How can I add PKCE to the standalone client example?

[sairus7]

This example works for me only with PKCE disabled on identity server side: https://github.com/tanmaykm/OpenIDConnect.jl/blob/master/tools/oidc_standalone.jl
(look also for previous issue #21)

When I try my client_ids for which PKCE is enabled, token request returns invalid_grant error.
Also I noticed that flow_request_authorization_code and flow_get_authorization_code exported from this library are not used in this example. And I don't understand why or where to add them.

[tanmaykm]

I think the issue stems from the fact that oidc_standalone.jl uses a javascript library to do part of the flow. The js client generates its own challenge and verifier which the Julia part does not know and is unable to complete the pkce negotiation.