Create Stream table

[iCantSneed]

The Stream table will aid in quickly retrieving superchats belonging to a specific stream. It should contain these columns:

• id - should not be sequential. Preferably should be the chat ID.
• prev - the Stream id preceding this one, or null if this is the first one.
• date - the date when the stream occurred, in EST timezone

The Superchat table needs to be altered to add a stream column and make it indexable.

The cached superchats should contain the Stream id and, more importantly, the prev id, so it can be delivered to the UI. The UI can use the prev id to retrieve superchats for the previous stream, the previous stream can provide the stream id prior to that one, and so on.

To be completed after #50.

[iCantSneed]

Migrations:

• Group superchats by date and insert into the Stream table with a unique ID

  
  INSERT INTO stream (date, id) SELECT date(convert_tz(created, '+00:00', '-06:00')) as date, floor(rand() * 0x10000000) as id FROM `superchat` GROUP by date

• Populate prev_id based on previous rows' id

  
  UPDATE superchat A set A.prev_id = (select B.id from superchat B where B.date < A.date order by B.date DESC limit 1)