feat(auth): Added code flow support for OIDC flow.

[xil222]

RELEASE NOTE: Added code flow support for OIDC flow(previously only support idToken flow).
RELEASE NOTE: Defined OAuthResponseType for specifying responseType either idToken or code.
RELEASE NOTE: Defined two new error codes: INVALID_OAUTH_RESPONSETYPE and MISSING_OAUTH_CLIENT_SECRET.

[hiranya911]

Looks good. I mostly had nits. There might be couple of edge cases that need better handling and some tests.

[hiranya911]

Thanks for making the changes. Looks pretty good. Just one last suggestion to cleanup the large loop in the implementation.

[hiranya911]

Thanks. LGTM 👍

[bojeil-google]

Change looks good. Just 2 minor issues.

[bojeil-google]

I am concerned about legacy customers and would recommend keeping a test without clientSecret and responseType. Can you add new tests instead of modifying the existing ones?

[xil222]

I add tests for createOAuthIdpConfig and updateOAuthIdpConfig

[egilmorez]

One optional nit if it's not too big a PITA to regen the reference.

Thanks!

[egilmorez]

This comment could be improved. Suggest:

" * One of the following must be true:

• If code is set to true, then we are doing code flow.
• If dToken is set to true, then we are doing ID token flow."

(Assuming that backticks are rendered as code font, and that "ID token flow" is a thing, separate from the literal idToken flag.