adds an option when enabling referrals to use the duration of the source
invited (i.e., months, days, hours) for the referral invite. If enabled,
the user won't be able to make a new referral link after it expires. For
referrals enabled for new users via a profile, the clock starts ticking
as soon as the account is created.
moving to a DB meant empty slices in the Configuration & Policy structs
were being stored as null, and striking a nerve with Jellyfin.
Mediabrowser library change fixed that by de-nulling them itself, and a
new bool field called "Homescreen" is now used to decide if a profile
has a homescreen layout stored or not. This field is hopefully correctly
filled in during migration.