Issue a warning if sizelimit or number of entries is higher than max_input_vars PHP ini setting

Description

When adding 1000+ users to a group, I got this error:

Fatal error: Uncaught FusionDirectoryException: CSRF protection token missing in /usr/share/fusiondirectory/include/class_CSRFProtection.inc:29 Stack trace: #0 /usr/share/fusiondirectory/html/main.php(59): CSRFProtection::check() #1 {main} thrown in /usr/share/fusiondirectory/include/class_CSRFProtection.inc on line 29

Distribution Name and Version

Debian 10

FusionDirectory Version

1.3.1

PHP version used

7.3.27

Origin of php packages

Distribution packages

Steps to Reproduce

1. Create a group
2. Add 1000+ members

Expected behavior: Members should be added to the group

Actual behavior: PHP Fatal Error

Reproduces how often: 100% of time

Additional Information

None.