Database transactions hold onto connections, and `pubsub.Publish` tries
to acquire a connection of its own. If the latter is called within a
transaction, this can lead to connection exhaustion.
I plan two follow-ups to this PR:
1. Make connection counts tuneable
https://github.com/coder/coder/blob/main/cli/server.go#L2360-L2376
We will then be able to write tests showing how connection exhaustion
occurs.
2. Write a linter/ruleguard to prevent `pubsub.Publish` from being
called within a transaction.
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Signed-off-by: Danny Kopping <dannykopping@gmail.com>
a646478aed