Add initial Drone CI configuration

[jdbaldry]

• test and build on all events and references
• release on tag events

Currently this uses our internal Drone server but that can be changed to the public drone server once the repository is made public.

[jdbaldry]

I didn't actually see that this repo already had GitHub actions for doing the test, lint, and build steps. Clearly, I need to implement cross compilation for this PR to replace those existing workflows. The release pipeline should still be valuable in the mean time but I imagine we will want the cross build testing in Drone before this is merged.

[simonswine]

This looks very good already, many thanks. Will have a closer look tomorrow.

I need to implement cross compilation

Do not worry about this, I doubt we need anything apart from Linux amd64. I just copied it from somewhere else 🙂

[jdbaldry]

Whoops, I didn't see your comment come through before I implemented cross compilation!

Even though cross compilation isn't strictly necessary, it was likely we were going to need to create and maintain a build-image for CI purposes anyway so it wasn't wasted effort.

If you want to inspect the drone pipelines you can go to http://drone.grafana.net/grafana/prometheus-pulsar-remote-write/ and you can also look at the release vtest2 for the result of the release pipeline. Once we are happy with this, I can make sure that we have a Docker Hub image under the grafana org instead of my own account and I'll clean up the test release tags.

[simonswine]

This looks (almost) prefect. Thank you for your work on that 👍

I think the next steps (as far as I would see them):

• Build and push a docker image for linux-amd64
• Move to a docker.io/grafana repo
• Disable Github actions

[jdbaldry]

@simonswine I think I've now addressed all comments so this should be good to go now :)

[simonswine]

All good now, thanks for this 🎉

Feel free to push the button @jdbaldry