Add audience parameter to token request

This is for making oidc authentication compatible with Auth0
https://auth0.com/docs/api-auth/tutorials/client-credentials

models/auth/oidc.go

@@ -17,6 +17,7 @@ package auth
 import (
 	"context"
 	"fmt"
+	"net/url"
 
 	"github.com/fatedier/frp/models/msg"
 
@@ -152,6 +153,7 @@ func NewOidcAuthSetter(baseCfg baseConfig, cfg oidcClientConfig) *OidcAuthProvid
 		ClientSecret:   cfg.OidcClientSecret,
 		Scopes:         []string{cfg.OidcAudience},
 		TokenURL:       cfg.OidcTokenEndpointUrl,
+		EndpointParams: url.Values{"audience": []string{cfg.OidcAudience}},
 	}
 
 	return &OidcAuthProvider{