identifiers: Add to_dict method to SWHID class

This is needed for the /api/1/resolve/(swhid)/ endpoint implementation of swh-web (see D3467).

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Migrated from D3465 (view on Phabricator)

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Patch application report for D3465 (id=12264)

Rebasing onto 52ef52ea...

Current branch diff-target is up to date.

Changes applied before test

commit 0547a516e6b1d197c8a748b8b4d1fb4bacf3ab79
Author: Antoine Lambert <antoine.lambert@inria.fr>
Date:   Wed Jul 8 16:18:40 2020 +0200

    identifiers: Add to_dict method to SWHID class

See https://jenkins.softwareheritage.org/job/DMOD/job/tests-on-diff/121/ for more details.

mentioned in merge request swh-web!1007 (closed)

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approved this merge request

What's wrong with attr.asdict?

Merge request was merged

closed

! In !287 (closed), @vlorentz wrote: What's wrong with attr.asdict?

Nothing but I prefer to wrap its use in an utility method rather than importing the attr module in client code.