Moving around 'borrowed' header files

[argmarco-tkd]

Rationale for this change

This is a minor code reorganization. We're moving from parquet/encryption/external and into parquet/encryption/external/borrowed header files (*.h) which are copied from other projects/repos.

The files we're moving: dbpa_interface.h, enums.h, span.hpp

Are these changes tested?

Code builds and tests pass.

[github-actions]

Thanks for opening a pull request!

If this is not a minor PR. Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

Then could you also rename the pull request title in the following format?

GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

MINOR: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[sofia-tekdatum]

The change LGTM, just not sure about the "borrowed" name? We're not really borrowing them, they're more like an external integration.

Ugh, naming sucks.

[avalerio-tkd]

How about "shared" ?

[argmarco-tkd]

Should have added context. The plan here is for these files to (once we move to dev_phase2 and/or protegrity/main) to be "properly" imported into the project (e.g. via an actual "includes" such as /usr/include directory, instead of having them copied here.

I evaluated several names. Settled on 'borrowed' as a forcing function to ensure we do the proper thing with these header files. We already have a task defined to do just that - protegrity/DataBatchProtectionService#64

Happy to change the name. These are some of the options I evaluated:

third_party
vendored
imported
borrowed
shared

[sofia-tekdatum]

Ok, if the borrowed name is meant to be uncomfortable so we remember to change it, plus there's a task for it as well, then I'm good with it. Thanks!