Channel and show ids

Every channel has one id across all our sources, taken from the open iptv-org registry where it has one, such as ch_jw83a3xg. A channel that sends its guide under different names in different feeds still has one id.

Shows and episodes carry the TVmaze ids, so you can join them to anything else that uses those. When two channels or shows turn out to be one, the old id answers 410 id_merged with the new one in meta.moved_to.