* Add --oidc-extra-url-params argument
This accepts a comma-separated list of key-value pairs that will be
added to get token requests as query string parameters.
Closes#254.
* Refactor
- move code setting the extra params to the authorization code flow specific functions (it is not needed in ROPC flow)
- add unit tests
- rename flag to --oidc-auth-request-extra-params
- add description to README.md
* Add integration test for --oidc-auth-request-extra-params
Co-authored-by: Hidetake Iwata <int128@gmail.com>