invalid_client when no Client Secret sent for PKCE about django-oauth-toolkit

[serra-pablo]

Just to confirm that this breaks the standard I reviewed the OAuth2 documentation. It says in section 3.2 that:
"Parameters sent without a value MUST be treated as if they were omitted from the request."
So not sending the parameter, or putting in a null/empty value should be treated the same. Even though it is not completely clear what they mean with 'without a value'.

https://datatracker.ietf.org/doc/html/rfc6749#section-3.2

This is confirmed in section 2.3.1 where it mentions the client_secret parameter MAY be omitted by clients if empty.
https://datatracker.ietf.org/doc/html/rfc6749#section-2.3.1