Use JSONB instead of arrays for requestedGroupIds

[flvndvd]

More context here.

PostgreSQL doesn't support jagged arrays (array of arrays such that member arrays can be of different sizes). The only alternative is to use JSONB field.

[spolu]

JSONB or pad with zeros. But let's avoid padding with the last value as this can likely grow indefeinitely in the current state of affair if we add a group to a padded one.