InternalDeduplicate sents events from `events` to the `deduplicated` channel, but deduplicates events that are sent multiple times.

NewChangeFeedConnection opens a new connection to the database and enables the CHANGEFEED feature.

WatchChangeFeed sends changed rows on the channel.

WatchFile spawns a background goroutine to watch file, reporting any changes to c.

ErrSchemeUnknown is just for checking with errors.Is().