add coverage reporting for e2e tests

[nak0f]

fixes #1533

[nak0f]

This works in my local but didn't work in Github CI. Most likely, kind host volume mounts don't work in here. I will try to solve this with something else.

[nak0f]

Below you can see output from the fist successful run:

--- E2E test coverage report
go tool covdata percent -i=/home/runner/work/logging-operator/logging-operator/build/_test_coverage/covdatafiles
	github.com/kube-logging/logging-operator		coverage: 57.7% of statements
	github.com/kube-logging/logging-operator/controllers/extensions		coverage: 5.9% of statements
	github.com/kube-logging/logging-operator/controllers/logging		coverage: 75.5% of statements
	github.com/kube-logging/logging-operator/pkg/compression		coverage: 0.0% of statements
	github.com/kube-logging/logging-operator/pkg/mirror		coverage: 65.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources		coverage: 100.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/annotation		coverage: 0.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/configcheck		coverage: 76.7% of statements
	github.com/kube-logging/logging-operator/pkg/resources/eventtailer		coverage: 0.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/fluentbit		coverage: 60.5% of statements
	github.com/kube-logging/logging-operator/pkg/resources/fluentd		coverage: 62.7% of statements
	github.com/kube-logging/logging-operator/pkg/resources/hosttailer		coverage: 0.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/kubetool		coverage: 25.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/loggingdataprovider			github.com/kube-logging/logging-operator/pkg/resources/model		coverage: 68.3% of statements
	github.com/kube-logging/logging-operator/pkg/resources/nodeagent		coverage: 0.4% of statements
	github.com/kube-logging/logging-operator/pkg/resources/prometheus-operator		coverage: 0.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/syslogng		coverage: 57.1% of statements
	github.com/kube-logging/logging-operator/pkg/resources/templates		coverage: 75.0% of statements
	github.com/kube-logging/logging-operator/pkg/resources/volumepath		coverage: 0.0% of statements
	github.com/kube-logging/logging-operator/pkg/webhook/podhandler		coverage: 0.0% of statements

[pepov]

@nak0f this looks good, do you think this is now ready for review?

[nak0f]

@nak0f this looks good, do you think this is now ready for review?

I was thinking of merging these with unit test coverage. Maybe adding a CI step with a coverage check. Is it better to keep this separate and leave these for future?

[pepov]

whatever works for you, no hurries