bullet proof smtp

[supersven]

Problem to be solved:
When an SMTP server was misconfigured in the brig configuration or was misbehaving itself, brig was hanging on startup without any useful logs.

Changes in this PR:

• Add tests for sending via SMTP. The used SMTP server is postie. Unfortunately, the current version of postie wasn't compatible to our GHC version due to outdated dependencies. I've updated postie's dependencies and brought it upstream (alexbiehl/postie@c927023). However, these changes are neither on Hackage nor in nixpkgs, yet. That's why I had to add a Nix override...

• The entry and exit (with result) are now logged. I've separated the log logic from other concerns.

• In the initialization code, logs are flushed before any error is thrown.

• I've added a timeout with a big tolerance to every action. This should prevent use from hanging due to endlessly delaying SMTP servers and other network obscurities.

Behaviour:

• Despite logging and an additional exception on timeout, the observable behavior should be unchanged. All caught exceptions are logged and then re-thrown as is.

Output without and with this patch:

When the SMTP server isn't reachable on startup.
Before:

brig: Network.Socket.connect: <socket: 13>: does not exist (Connection refused)

Now:

brig: Failed to establish test connection with SMTP server: CaughtException Network.Socket.connect: <socket: 13>: does not exist (Connection refused)
CallStack (from HasCallStack):
  error, called at src/Brig/SMTP.hs:116:7 in brig-2.0-inplace:Brig.SMTP
[brig] W, Checking test connection to localhost on startup : Caught exception : Network.Socket.connect: <socket: 13>: does not exist (Connection refused)

Where [brig] is logged output and brig: stderr/stdout.

Ticket: SQPIT-497

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[fisx]

i left some comments. looks good, but i think i want a guided tour on monday or so! :-) ping me!

[fisx]

👍

[fisx]

Suggested change

	let resultLog = case e of
	SMTPUnauthorized ->
	("Failed to establish connection, check your credentials." :: String)
	SMTPConnectionTimeout -> ("Connection timeout." :: String)
	let resultLog = show e

? not sure about this one :)

[supersven]

I'd argue that it's fine to be a bit more chatty in log messages. Finally, they are meant to be interpreted by Ops people outside of Wire.