Use the ClientSchedule data structure for deserialising and tracking
edit state on the client instead of trying to directly deal with the
ApiSchedule type which is not build for ease of edits or rendering.
Rename and refactor the types passed over the API to be based on an
entity that's either living or a tombstone. A living entity has a
deleted property that's either undefined or false, while a tombstone
has a deleted property set to true. All entities have a numeric id
and an updatedAt timestamp.
To sync entities, an array of replacements are passed around. Living
entities are replaced with tombstones when they're deleted. And
tombstones are replaced with living entities when restored.