I have installed the extension and tried to invite a user.
There were database errors about no default value given. Database looks like this:
```
MariaDB [akademie_mediawiki]> show columns FROM invitesignup;
+------------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+------------------+------+-----+---------+-------+
| is_hash | varbinary(40) | NO | PRI | NULL | |
| is_inviter | int(10) unsigned | NO | | NULL | |
| is_invitee | int(10) unsigned | NO | | 0 | |
| is_email | varbinary(255) | NO | | NULL | |
| is_when | binary(14) | NO | | NULL | |
| is_used | binary(14) | NO | | NULL | |
| is_groups | longblob | NO | | NULL | |
+------------+------------------+------+-----+---------+-------+
7 rows in set (0.001 sec)
```
It seems as if it is not about no but about a wrong default value. I got this working by
```
MariaDB [akademie_mediawiki]> ALTER TABLE invitesignup ALTER COLUMN is_invitee SET DEFAULT 0;
Query OK, 0 rows affected (0.003 sec)
Records: 0 Duplicates: 0 Warnings: 0
MariaDB [akademie_mediawiki]> ALTER TABLE invitesignup ALTER COLUMN is_used SET DEFAULT 0;
Query OK, 0 rows affected (0.004 sec)
Records: 0 Duplicates: 0 Warnings: 0
```
Maybe null should be allowed as value?
This fixed the original errors. After that I received another error message:
```
[c764da093dfa911cc482d649] /wiki/Special:InviteSignup ArgumentCountError: Too few arguments to function EmaillingJob::__construct(), 2 passed in /var/www/html/w/extensions/InviteSignup/includes/SpecialInviteSignup.php on line 224 and exactly 3 expected
Backtrace:
from /var/www/html/w/includes/jobqueue/jobs/EmaillingJob.php(36)
#0 /var/www/html/w/extensions/InviteSignup/includes/SpecialInviteSignup.php(224): EmaillingJob->__construct()
#1 /var/www/html/w/extensions/InviteSignup/includes/SpecialInviteSignup.php(78): SpecialInviteSignup::sendInviteEmail()
#2 /var/www/html/w/includes/specialpage/SpecialPage.php(719): SpecialInviteSignup->execute()
#3 /var/www/html/w/includes/specialpage/SpecialPageFactory.php(1672): MediaWiki\SpecialPage\SpecialPage->run()
#4 /var/www/html/w/includes/actions/ActionEntryPoint.php(502): MediaWiki\SpecialPage\SpecialPageFactory->executePath()
#5 /var/www/html/w/includes/actions/ActionEntryPoint.php(145): MediaWiki\Actions\ActionEntryPoint->performRequest()
#6 /var/www/html/w/includes/MediaWikiEntryPoint.php(199): MediaWiki\Actions\ActionEntryPoint->execute()
#7 /var/www/html/w/index.php(58): MediaWiki\MediaWikiEntryPoint->run()
#8 {main}
```
I did not try to fix this error and stop trying this extension for now.
The third argument seems to have been added in recent versions.