Integration tests

[wvengen]

• Add initial tests
• CI for Docker (running locally)
• CI for Kubernetes (running locally)
• Fix jobs on Kubernetes CI being stuck in scheduled
• CI for running scrapyd-k8s in Kubernetes (testing kubernetes.yaml)
• Add spider to example spider project that returns static data (or run from cache)
• Finish tests --> as part of other issues

Possible next steps:

• Test job cancel while job is pending (needs something to create a job without starting it)
• Test http auth (needs config file change and daemon restart, so perhaps different method)
• Test if values in secret and configmap are passed through to the spider (*)
• Test if pull secret is picked up
• Test if schedule spider arguments are passed through to the spider (*)
• Test if schedule spider settings are passed through to the spider (*)

(*) May need changes to the example spider, e.g. returning ENV, spider settings and spider arguments in static spider or a new debug spider or so.

[vlerkin]

Thank you, nicely done! Also very valuable for me to learn this level of testing:)