fix(dev): fix hot reloading and Localstack port

[mantariksh]

Problem

1. Server hot reloading has been broken in the dev environment for a couple of months.
2. A recent Localstack upgrade (v0.11.5) broke the local S3 service on the S3 port 4572, which is also due to be deprecated.

Solution

Hot reloading

Running ts-node-dev with the --debug flag showed the following issue:

The SIGTERM was somehow failing for the child process. To fix this, I added the --exit-child flag (docs).

Localstack

Since the ports for individual services are due to be deprecated anyway, I thought we should try to switch to the edge port 4566. However, when I tried to switch, I got the following error:

formsg-localstack | 2020-09-16T09:27:37:INFO:localstack.services.edge: Unable to find forwarding rule for host "localhost:4566", path "/", target header "", auth header "", data "b''"

I figured this was probably related to the fact that we had a hackish way of initialising our S3 buckets. Rather than using the documented way of initialising AWS resources, we were using init-localstack.sh to repeatedly ping localhost:4572 until Localstack was ready, before initialising the S3 buckets. Since we are now using the latest version of Localstack which supports initialisation scripts, I removed the pinging code and added the bucket initialisation code to /docker-entrypoint-initaws.d.

Unsolved mysteries

Local emails are still broken for me due to the same error encountered by @frankchn which necessitated #285. However, not everyone seems to be facing the same issue, so this is likely due to some local configuration problem.

[karrui]

AHHHH THIS IS GREAT