Capacity to add new itemtypes on schema

[trasher]

No description provided.

[trasher]

To be reviewed per commit.
If someone has an idea to prevent latest commit (phpstan complains about missing index 1 in result, but that cannot happen), I'll take it.

[stonebuzz]

IMHO

you can't assume that index 1 exists and access it directly.

you need another isset (like you did) or array_key_exists

or null coalecing operators

$known_itemtypes = explode('|', $known_itemtypes[1] ?? '');

[trasher]

Keeping isset() is fine, it's useless but it does not hurts :)