* Automated test towards PHPStan level 6
Contributes to https://github.com/FreshRSS/FreshRSS/issues/4112
With this automated tests, files that are passing Level 6 are tested to avoid regressions towards Level 5 (which is the current baseline for the whole code-base)
It is included when calling `make test-all` or can be called specifically by `composer run-script phpstan-next`
* Test and example with 3 new passing files
Fix regressions from https://github.com/FreshRSS/FreshRSS/pull/4561
Example:
```
PHP Fatal error: Uncaught TypeError: Argument 1 passed to checkToken() must be an instance of FreshRSS_UserConfiguration, instance of Minz_Configuration given, called in /var/www/FreshRSS/p/api/greader.php on line 1091 and defined in /var/www/FreshRSS/p/api/greader.php:223
Stack trace:
#0 /var/www/FreshRSS/p/api/greader.php(1091): checkToken()
#1 {main}
thrown in /var/www/FreshRSS/p/api/greader.php on line 223
```
Improvement of https://github.com/FreshRSS/FreshRSS/pull/4110
* Custom logo HTML
Add option for custom HTML logo/title in the main Web UI view.
Can potentially be different per user.
#fix https://github.com/FreshRSS/FreshRSS/pull/3830/files#r850472247
* logo_html in main config
With new `./data/config.custom.php` to provide custom values before install
* Docker documentation
* whitespace
* Auto relax CSP to allow images for HTML logo
* Documentation
* add HTTP_REMOTE_USER header for auth
* add ip whitelist for HTTP_REMOTE_USER header
* add IPv6 support for header auth
* fix formatting
* A few fixes
* Add some default trusted sources
* Fix IPv6 doc
* More standard header names
Co-authored-by: Alexandre Alapetite <alexandre@alapetite.fr>
