workflow step name in keyFormat for archiveLogs

Summary

I would like to use {{step.name}} in keyFormat definition when using archiveLogs: true.

Motivation

Currently the only way to separate the logs from a single workflow and preventing Argo from overwrite the logs from the preceding workflow steps I have to use {{pod.name}}. pod.name does not provide information about the step the log file was created by. This requires searching through all log files in each pod name folder to find the right output.

Proposal

When setting keyFormat: {{workflow.label.data-id}}/{{workflow.name}}-{{workflow.creationTimestamp}}/{{step.name}}.log Argo should create a single log file named after the steps name in that specified folder.
Example:
"A123/preprocessing-2020-07-08 12:11:53 +0000 UTC/merge-files.log"
This requires that:

1. Argo detects "keyFormat" ends with ".log" so it does not create a subfolder with file "main.log"
2. Argo is able to translate the variable "step.name".

Message from the maintainers:

If you wish to see this enhancement implemented please add a 👍 reaction to this issue! We often sort issues this way to know what to prioritize.

Start from the archiveLogs and keyFormat handling described in the issue, including template variable translation and the requested .log behavior. Trace how archived workflow logs currently derive pod folders and main.log, then verify that step.name produces one step-named log file in the requested folder.