Minz allow parallel sessions (#3096)

* Minz allow parallel sessions

#fix https://github.com/FreshRSS/FreshRSS/issues/3093

* Array optimisation

* Array optimisation missing

* Reduce direct access to $_SESSION except in install process

* Fix session start headers warning

* Use cookie only the first time the session is started:
`PHP Warning:  session_start(): Cannot start session when headers
already sent in /var/www/FreshRSS/lib/Minz/Session.php on line 39`

* New concept of volatile session for API calls

Optimisation: do not use cookies or local storage at all for API calls
without a Web session
Fix warning:

```
PHP Warning:  session_destroy(): Trying to destroy uninitialized session
in Unknown on line 0
```

* Only call Minz_Session::init once in our index

It was called twice (once indirectly via FreshRSS->init())

* Whitespace

* Mutex for notifications

Implement mutex for notifications
https://github.com/FreshRSS/FreshRSS/pull/3208#discussion_r499509809

* Typo

* Install script is not ready for using Minz_Session

1 files changed, 8 insertions, 3 deletions

diff --git a/app/install.php b/app/install.php
index bed2a8383..5093b45a6 100644
--- a/app/install.php
+++ b/app/install.php
@@ -163,9 +163,14 @@ function saveStep2() {
 
 		$ok = false;
 		try {
-			Minz_Session::_param('currentUser', $config_array['default_user']);
-			$ok = initDb();
-			Minz_Session::_param('currentUser');
+			$_SESSION['currentUser'] = $config_array['default_user'];
+			$error = initDb();
+			unset($_SESSION['currentUser']);
+			if ($error != '') {
+				$_SESSION['bd_error'] = $error;
+			} else {
+				$ok = true;
+			}
 		} catch (Exception $ex) {
 			$_SESSION['bd_error'] = $ex->getMessage();
 			$ok = false;