Add CONTRIBUTING.md and fix CI workflow step dependencies (#211)

* Add CONTRIBUTING.md

* Gate e2e tests on Helm lint

Author: sd109

.github/workflows/test-pr.yaml

@@ -39,13 +39,14 @@ jobs:
 
   # This job exists so that PRs from outside the main repo are rejected
   fail_on_remote:
+    needs: [unit_tests, lint]
     runs-on: ubuntu-latest
     steps:
       - name: PR must be from a branch in the azimuth-cloud/cluster-api-janitor-openstack repo
         run: exit ${{ github.event.pull_request.head.repo.full_name == 'azimuth-cloud/cluster-api-janitor-openstack' && '0' || '1' }}
 
   publish_artifacts:
-    needs: [unit_tests,fail_on_remote]
+    needs: [fail_on_remote]
     uses: ./.github/workflows/build-push-artifacts.yaml
     with:
       ref: ${{ github.event.pull_request.head.sha }}

CONTRIBUTING.md

@@ -0,0 +1,22 @@
+# Contributing
+
+We welcome contributions and suggestions for improvements to this code base.
+Please check for relevant issues and PRs before opening a new one of your own.
+
+## Making a contribution
+
+### Helm template snapshots
+
+The CI in this repository uses the Helm
+[unittest](https://github.com/helm-unittest/helm-unittest) plugin's
+snapshotting functionality to check PRs for changes to the templated manifests.
+Therefore, if your PR makes changes to the manifest templates or values, you
+will need to update the saved snapshots to allow your changes to pass the
+automated tests. The easiest way to do this is to run the `helm unittest` command
+inside a docker container from the repo root.
+
+```
+docker run -i --rm -v $(pwd):/apps helmunittest/helm-unittest chart -u
+```
+
+where the `-u` option is used to update the existing snapshots.