Update module to use auth0/auth0-php version 8.x

Thanks for the work @polynya and @aneek

One thing I was noticing when comparing the previous set of changes is that I don't think the offline access was set up correctly and I think this solves the issue as per https://auth0.com/docs/secure/tokens/refresh-tokens/get-refresh-tokens you need to specify offline_access in the scopes if your permitting offline access

```
diff --git a/src/Controller/AuthController.php b/src/Controller/AuthController.php
index 1a93a6f..95d389c 100644
--- a/src/Controller/AuthController.php
+++ b/src/Controller/AuthController.php
@@ -231,7 +231,7 @@ class AuthController extends ControllerBase {
$this->redirectForSso = (bool) $this->config->get(AuthController::AUTH0_REDIRECT_FOR_SSO);
$this->offlineAccess = (bool) $this->config->get(AuthController::AUTH0_OFFLINE_ACCESS);
$this->currentRequest = $request_stack->getCurrentRequest();
-
+ $scopes = explode(' ', AUTH0_DEFAULT_SCOPES);
$sdk_configuration = new SdkConfiguration([
'domain' => $this->helper->getAuthDomain(),
'clientId' => $this->clientId,
@@ -239,6 +239,7 @@ class AuthController extends ControllerBase {
'cookieSecret' => $this->cookieSecret,
'redirectUri' => "$base_url/auth0/callback",
'persistUser' => FALSE,
+ 'scope' => ($this->offlineAccess ? array_merge($scopes, ['offline_access']) : $scopes),
]);
$transient_store = new SessionStore($sdk_configuration);
$sdk_configuration->setTransientStorage($transient_store);
```

Just flagging that I have tested this with the change I mentioned above on a client site and login works successfully. One thing I would suggest is that this should probably be done as a 4.x version given the change in the SDK version and also we need to highlight in the release notes that the auth0_cookie_secret needs to be configured probably prior to the upgrade otherwise can get a fatal error

Thank you @polynya and @seamus_lee! I rebased MR3 and adding also the bit about the offlines scopes and a contribution from me to fill the cookie secret in a hook_update_N and hook_install.
I kept the commits unsquashed credit where credit is due.

Automatically closed - issue fixed for 2 weeks with no activity.