- The redirection URI (callback handler) receives the OAuth2 callback, verifies the state parameter, and obtains a Token.
- Using the id_token the callback handler further talks to Google OAuth2 Token URL to obtain an JWT id_token.
- Once obtained the JWT id_token is further sent to STS endpoint i.e MinIO to retrieve temporary credentials.
- Temporary credentials are displayed on the browser upon successful retrieval.

	}

	claims["exp"] = time.Now().UTC().Add(defaultExpiryDuration).Unix() // update with new expiry.
	return nil
}

const (
	audClaim = "aud"
	azpClaim = "azp"
)

// Validate - validates the id_token.
func (r *Config) Validate(ctx context.Context, arn arn.ARN, token, accessToken, dsecs string, claims jwtgo.MapClaims) error {
	jp := new(jwtgo.Parser)
	jp.ValidMethods = []string{
		"RS256", "RS384", "RS512",

	ResponseTypesSupported           []string `json:"response_types_supported,omitempty"`
	SubjectTypesSupported            []string `json:"subject_types_supported,omitempty"`
	IDTokenSigningAlgValuesSupported []string `json:"id_token_signing_alg_values_supported,omitempty"`
	ScopesSupported                  []string `json:"scopes_supported,omitempty"`
	TokenEndpointAuthMethods         []string `json:"token_endpoint_auth_methods_supported,omitempty"`

	// code, which we now have in `lastReq`. Exchange it for a JWT id_token.
	q := lastReq.URL.Query()
	// fmt.Printf("lastReq.URL: %#v q: %#v\n", lastReq.URL, q)
	code := q.Get("code")
	oauth2Token, err := oauth2Config.Exchange(ctx, code)
	if err != nil {
		return "", fmt.Errorf("unable to exchange code for id token: %v", err)
	}

	rawIDToken, ok := oauth2Token.Extra("id_token").(string)
	if !ok {