fix: Temporal service waits for db to be healthy

[tomasfarias]

Problem

In the CI logs of a recent failure we see:

posthog-temporal-1     | 2023-06-15T11:15:54.088Z	ERROR	Unable to create SQL database.	{"error": "unable to connect to DB, tried default DB names: postgres,defaultdb, errors: [pq: the database system is starting up pq: the database system is starting up]", "logging-call-at": "handler.go:94"}

Changes

Let's add a healthcheck to the db service and wait for it to be healthy for temporal to run.

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

How did you test this code?

[hazzadous]

@tomasfarias I'm going to yolo this in! See if it doesn't help with the failures.

[tomasfarias]

@hazzadous Thanks for reviewing! Just wanted to make sure someone looked at my docker-compose changes in case I break the stack.

All for merging this in and checking out if it helps!

[hazzadous]

Yeah sorry I woke up trigger happy :/ I don't think it's a good thing. Very rude.

[tomasfarias]

@hazzadous I didn't take anything the wrong way, I'm all for merging stuff. Thank you 😺