This adds PR comments with digger run fails

[ben-of-codecraft]

When a digger job would fail, the error message in the log did not show the output, it only reported it to the backend API. This information is helpful in debugging problems.

Additionally, this adds a PR comment with the error message.

[ben-of-codecraft]

This is what is failing

    license_test.go:10: 
        	Error Trace:	/home/runner/work/digger/digger/libs/license/license_test.go:10
        	Error:      	Received unexpected error:
        	            	license key is not valid: {"valid":false}
        	Test:       	TestLicenseKeyChecker
--- FAIL: TestLicenseKeyChecker (0.93s)
FAIL
FAIL	github.com/diggerhq/digger/libs/license	0.932s

Not sure why this one is failing any thoughts?

[motatoes]

This looks great, but we prefer to use reporter object when reporting since it will append it to the same comment for the job isntead of creating a new comment. See example usage here:

digger/cli/pkg/digger/digger.go

Line 321 in 3496e66

_, _, err = reporter.Report(planSummary, coreutils.AsComment("Terraform plan summary"))