feat: support add additional params for OIDC

[blizard863]

#2802
#1714

[blizard863]

This PR is tested by standard OAuth 2.0, Auth0 and Authing. I think it's reasonable.

[blizard863]

Hello @addisonj I saw your PR #2802 .

I think the auth0 is using not-standard OAuth2.0.

https://datatracker.ietf.org/doc/html/rfc6749
https://community.auth0.com/t/client-credentials-with-postman/34282/5

I warry about if there are auth1, auth2 companies which also need audience parameters but its value is not equal "cfg.OidcAudience" but "foobar". So I think hard code in frp is not suitable. I make it configurable.

And also, I register a auth0 service account. In my PR, I test as follow.

frps.ini

authentication_method = oidc
oidc_issuer = https://dev-xxx.us.auth0.com/
oidc_audience = https://dev-xxx.us.auth0.com/api/v2/

frpc.ini
authentication_method = oidc
oidc_client_id = pExxxKqoxxxBH
oidc_client_secret = F3492WS5pxxxxx8OG83DWxxxxx5nP3Oe-Lxcaoxxxx
oidc_audience = ""
oidc_token_endpoint_url = https://dev-xxx.us.auth0.com/oauth/token
oidc_additional_audience = https://dev-xxx.us.auth0.com/api/v2/   // It will be set by frp  audience=<value> 

It pass test in auth0 service.

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@fatedier @GuyLewin WDYT ?

[addisonj]

@bingtianbaihua I think this seems reasonable. I was thinking of something like this as well might be preferable. LGTM!

[blizard863]

@bingtianbaihua I think this seems reasonable. I was thinking of something like this as well might be preferable. LGTM!

@addisonj OK，I will refine my code and merge it these days. By the way you can close your PR.