Send error.transaction_id and error.parent_id only if there is trace_id

[eyalkoren]

What does this PR do?

Context - reported in the forum.
APM Server will reject Error events that contain parent_id and/or transaction_id but do not contain trace_id. This PR ensures that this restriction is enforced.
In addition, it provides logs to analyze the reason for getting error captures that are not adhering this.

Checklist

• This is a bugfix
  • I have updated CHANGELOG.asciidoc
  • I have added tests that would fail without this fix

[felixbarny]

Do you have a suspicion why there can be a trace context with a non-empty transaction id but an empty trace id? The only things that come to my mind are race conditions or visibility issues.

[eyalkoren]

Do you have a suspicion why there can be a trace context with a non-empty transaction id but an empty trace id? The only things that come to my mind are race conditions or visibility issues.

No clue 🙁 . This is why I added the logs and asked the reporting user to trigger it.
Sadly, the only thing that came to my mind was concurrency-related as well, but I am hoping it would be something easier to pinpoint. It may be related to the non-fully-dereferenced transactions somehow 🤷‍♂️

[ghost]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Build Cause: [Pull request #1537 opened]

• Start Time: 2020-11-25T10:00:47.704+0000

• Duration: 46 min 37 sec

Test stats 🧪

Test	Results
Failed	0
Passed	1617
Skipped	12
Total	1629