[APM] Add link between errors and transactions

[makwarth]

All agents but the RUM agent now supports transaction.id on errors. That means we can link from a transaction sample to the error occurrence that occurred during that transaction (if any). We'll also be able to link the other way, from an error occurrence to a transaction sample.
NB: A transaction can throw multiple errors.

[elasticmachine]

Pinging @elastic/apm-ui

[formgeist]

Will look into creating some initial design screens for this 👍

[formgeist]

Just a couple of thoughts around this; I immediately started thinking to add the links to the Transaction sample and Error occurrence KPIs area.

Transaction samples would show a link with number of error groups (as it could have multiple), which links to the Errors list with the selected sample's transaction.id added as filter. That way the user gets a list of all error groups involved in the sample recorded.

Error occurrences will show a Transaction sample link to the exact Transaction sample involved.

Transaction detail page

Errors list filtered by transaction.id

Error detail page

[makwarth]

@formgeist looks good 👍

[sorenlouv]

Nice! This should be pretty easy to implement!

[sorenlouv]

Btw. The transaction that is being linked to from the error details page might not exist due to sampling.

[formgeist]

@sqren That's due to the instrumentation of the particular service and sample settings. So it will happen for some but not all, right?

[sorenlouv]

Yes, exactly. It will only happen to those who enable sampling. And it will happen frequently for users with high sampling rates.

[formgeist]

I'll convert this to an implementation issue

[formgeist]

Created two issues for Transactions #21920 and Errors #21919