Rename attendees to getAttendeesRelation.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Add method to get a party by host access code.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Add a host to each created party.

Refactor constructors to become “DRYer”.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Change so a party is deleted eventually.

- Will also delete the associated songs.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>