Make it possible to create error logs that are picked up by GCP Error Reporting

Start by locating the special message-key handling in @google-cloud/logging-winston and its tests. Verify how stack_trace and @type are currently placed, then add coverage showing that the supported Error Reporting fields remain in the expected top-level log entry and are recognized by the relevant formatting behavior.

Library Name

@google-cloud/logging-winston

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What would you like to see in the library?

Context

We're running a NodeJS application in GCP and wish to have logs with severity/level 'ERROR' show up in GCP's Error Reporting service.

We are currently using the @google-cloud/logging-winston library to write log messages (as recommended by GCP). However, we are finding that this library prevents us to write log messages in the format that the Error Reporting service expects.

According to the Error Reporting service's documentation, a log entry would be picked up when one these are true:

1. the log entry's message contains a stack trace
2. the log entry contains certain specific fields (stack_trace or exception, or a specific @type value

Although 1 is possible, it will include a stack trace inside a plain text message field, which clutters up the logging quite a bit. This makes querying and organizing logs unnecessarily harder.
Using method 2 would be a huge improvement, however the @google-cloud/logging-winston library prevents us from doing that. When we try to add a stack_trace, exception of @type field, it gets moved in a metadata object instead, causing the Error Reporting service to ignore the log entry.

Proposal

The @google-cloud/logging-winston already defines certain special message keys which are not put into the metadata object (fields like logging.googleapis.com/trace, level etc.). I propose we add stack_trace and @type to that list as well, allowing us to properly format a log entry to be picked up by the Error Reporting service.

As an alternative, we could also introduce a new option field in @google-cloud/logging-winston which explicitly enables formatting a log entry to be picked up by the error reporter (something like 'formatForErrorReporting:true`?).

No response

Describe alternatives you've considered

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Additional context/notes

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