Rename flag to --oidc-pkce-method and improve docs

[int128]

Resolves #1227.
Resolves #858.

Changes

Flags

This changes the flag --oidc-use-pkce to --oidc-pkce-method. It does not change the default behavior.

• Before
  • PKCE is automatically used if the provider supports it.
  • --oidc-use-pkce forces to use PKCE.
• After
  • PKCE is automatically used if the provider supports it.
  • --oidc-use-pkce is deprecated. Equivalent to --oidc-pkce-method=S256.
  • --oidc-pkce-method is added. It forces to use PKCE. Default to --oidc-pkce-method=auto.

Docs

This also improves the docs:

• Remove the client secret from README
• Add PKCE section to usage

[gaeljw]

Thanks @int128 , really appreciate the clarifications 👍

[3deep5me]

Thanks!