Tests are failing, but they have been failing for a while in this repo. Seems not caused by this PR.

You can regenerate phpstan baseline in follow up PR

For the record, I had a look at the phpstan baseline. Based on the confluence doc I ended up with 3 un-ignorable errors:

Ignored error pattern #^Parameter \#1 \$filename of function file_put_contents expects string, string\|false given\.$# in path src/lib/FieldTypeProcessor/BinaryInputProcessor.php was not matched in reported errors.

Ignored error pattern #^Parameter \#2 \$string of function explode expects string, string\|null given\.$# in path src/lib/Server/Controller/Content.php is expected to occur 1 time, but occurred 4 times.

Ignored error pattern #^Parameter \#1 \$directory of function mkdir expects string, string\|false given\.$# in path tests/lib/FieldTypeProcessor/BinaryInputProcessorTest.php was not matched in reported errors.

How Andrew handled it in 4.6: ibexa/rest#141
Will need to get back to this.