chore(ci): test Docker images in CI

[YOU54F]

Maintainer Conveniences

• Updates Dockerfile
  • Dockerfile was relevant for pact-go v1, now updated and tested as part of CI
• Inability to use Docker in MacOS / Windows, means to run Pact Broker based tests, we need to use a hosted broker. This poses challenges for external contributors and the sharing of secrets, as using shared credentials in plain-text although convenient for our demo env, isn't best practise for actual end user use.
  • Provide a make pact_local command that skips publishing of pacts, and via setting SKIP_PUBLISH controls the provider verification test to either run a local or pact broker based verification. The publish code path is still covered by the linux runner. (there is probably a more elegant way of conditionally setting the values rather than a large if / else block

[coveralls]

coverage: 29.152% (+0.1%) from 29.056%
when pulling 07ffd2d on deps/Dockerfile
into 4c2079f on master.

[coveralls]

coverage: 29.152% (+0.1%) from 29.056%
when pulling 4125314 on deps/Dockerfile
into 4c2079f on master.

[YOU54F]

segfaults mentioned above resolved in #432

[coveralls]

coverage: 29.252% (+0.1%) from 29.134%
when pulling 7fe738e on deps/Dockerfile
into c80e188 on master.

[coveralls]

coverage: 29.365% (+0.2%) from 29.134%
when pulling e9056b2 on deps/Dockerfile
into c80e188 on master.

[YOU54F]

we need to install our signal handlers after starting our plugins. I wondered why we were still getting flakes after I had got it passing consistently first time before, and I went back and looked at my previous changes I'd tested and did a 😅

[coveralls]

coverage: 29.376% (+0.2%) from 29.134%
when pulling a272944 on deps/Dockerfile
into c80e188 on master.

[coveralls]

coverage: 29.134%. remained the same
when pulling 1d0359a on deps/Dockerfile
into c80e188 on master.

[coveralls]

coverage: 29.248%. remained the same
when pulling 5bbeb1a on deps/Dockerfile
into f3b61a7 on master.

[coveralls]

coverage: 29.248%. remained the same
when pulling 19ca6ef on deps/Dockerfile
into f3b61a7 on master.

[coveralls]

coverage: 29.248%. remained the same
when pulling fc2097e on deps/Dockerfile
into f3b61a7 on master.