Increase slash command timeout to 30 seconds

[mickmister]

Summary

The timeout for slash commands is currently 6 seconds, which is causing issues for the /gitlab webhook add command. This PR increases the timeout to 30 seconds, which is what is currently used for incoming http requests:

mattermost-plugin-gitlab/server/api.go

Line 31 in de004a9

requestTimeout = 30 * time.Second

Ticket Link

Fixes #374

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (de004a9) 32.20% compared to head (2d8303d) 32.20%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #375   +/-   ##
=======================================
  Coverage   32.20%   32.20%           
=======================================
  Files          21       21           
  Lines        3465     3465           
=======================================
  Hits         1116     1116           
  Misses       2242     2242           
  Partials      107      107           

Impacted Files	Coverage Δ
server/command.go	23.60% <ø> (ø)

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[spirosoik]

shouldn't be this configurable instead?

[mickmister]

@spirosoik In general our solution has been to increase this to 30 seconds in plugin projects. I think having this as a plugin config setting is surfacing an implementation detail, but I'm not opposed to having it configurable. We would want to support configuring the http timeout as well, and be consistent on other projects and apply it there too. What do you think?

[mickmister]

We'll defer QA, from offline discussion with @DHaussermann