"params" (and "extras", e.g. metadata) flow through each update function
and are changed if necessary. Since "extras" was added later and old
update functions don't return it, we need to ignore undefined values
-- or change every single update function in all content types.
* Update validateGroup in h4p.classes.php to allow subContentId into the data
* Fix h5p-content-upgrade-process.js to take into account isSubContent
Relates to: #HFP-285
Paal Joergensen
Oliver Tacke
Tom Arild Jakobsen
Frode Petterson
Svein-Tore Griff With