Update Dockerfile to use newer Alpine version

Alpine 3:11 -> 3.12

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Add no-dco label before closing no_newbies PRs

In a PR raised on the openfaas/faasd repo, the no-dco label
wasn't added, when it should have been. If the PR was re-
opened then it may be merged in error, even without the DCO.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Revert DCO status checking

The status checking behaviour introduced in alexellis#108 appears to
break the existing DCO checking, so this PR disables it.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Improve error handling and ordering of JWT code

The if statements have been changed in order, to check for
an error first, then fall back to normal functionality. This is
to make the code more Go-idomatic, and easier to read.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Print verbose rate-limits

Where possible, print rate limits along with the related
action in the GitHub API / SDK.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Add fail check for dco

Adding check which determines whether or not
there are existing commits which are unsigned.
The check is determined by the no-dco label.

Signed-off-by: Martin Dekov <mvdekov@gmail.com>

Fix typo in removing deprecated api endpoint

Github deprecated and api endpoint for auth tokens on apps, I previously
typed `apps/` and it should have been `app/`

This has been tested by running the broken container, verifying that it
did not work, then changing the `apps` to `app` and re-deploying - then
invoking a change on github that sent webhooks to my installation. After
the fix it worked, was given the 5k/hr rate limit and correctly added /
removed labels from PRs.

Signed-off-by: Alistair Hey <alistair@heyal.co.uk>

Update to call new github API

Github are moving an endpoint for access_tokens for github apps. This
moves to the new api url.
Reference: https://developer.github.com/changes/2020-04-15-replacing-create-installation-access-token-endpoint/

Signed-off-by: Alistair Hey <alistair@heyal.co.uk>

Don't panic, return errors

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Ignore the review_requested action on PRs

Reported by @rberrelleza where multiple comments were sent on
a PR.

okteto/okteto#733

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>