document contextual parts of persistent identifiers

see T1040 for details

the doc should be added to the persistent identifier page

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Migrated from T1041 (view on Phabricator)

mentioned in merge request swh-model!271 (closed)

assigned to @zack

marked this issue as related to swh/meta#1040 (closed)

added 2018-06-07-unesco-webui Documentation priority:High labels

mentioned in commit swh-model@bc30e8bc

closed