Update database schema

[oskarrough]

Update sql/init.sql with the following.

All tables should have these fields

• id (with uuid?)
• [x] created_at (https://github.com/internet4000/radio4000-cms/issues/7)
• [x] updated_at (https://github.com/internet4000/radio4000-cms/issues/7)

Tables to create

• [x] user
  • (no fields needed)
• [x] channel
  • name, slug, url, latitude, longitude
• [x] track
  • url, title, description, discogs_url

Junction tables to create

• [x] user_channel
  • user_id, channel_id, role
• [x] channel_track
  • channel_id, track_id, user_id

[oskarrough]

How about "cascades" e.g. deleting relationships automatically?

• on a userDelete, also delete channels where you are owner? Doesn't seem good. But delete user_channel where user_id = id
• on a channelDelete, also delete all tracks
• on a trackDelete, also delete channel_track
• what else?

[oskarrough]

We've proposed replacing channel.user_id with the junction table user_channel. That would make these policies invalid.

How would we update them?

create policy "User can insert their own channel."
  on channels for insert
  with check ( auth.uid() = user_id );

maybe?

create policy "User can insert their own channel."
  on channels for insert
  using ( 
    auth.uid() in (
        select user_id from user_channel where user_channel.user_id = auth.uid()
    )
  );

[oskarrough]

track is missing discogs url