Umbrella Tracking Issue: for --chown

[JeromeJu]

Actual behavior
There has been multiple open issues pointing to the lack of clarification of --chown behavior for Kaniko:

• Caching with the combination of COPY --from with RUN #1600
• COPY --chown fails image build with unknown user #1603
• COPY --chown=1001:0 . . copies directories as root #2035

Expected behavior
There should be clear instructions in Kaniko on specifically which commands could run with --chown. And these commands should run as expected.

• Currently, COPY --chown and ADD -chown are supported. (Support COPY --chown flag #962, Add support to --chown flag to ADD command (Issue #57) #1134)
• There is no support for Run --chown.

Current Kaniko version @ HEAD: v1.20.1

The expected outcome of this issue:

• Enhanced documentation for Kaniko users
• Patch bugs where needed for the COPY --chown usage
• Update existing open issues related and close out-dated requests