Implement PCI workflow model objects

[richard-jones]

• PR: [when the PR is created, put a link to it here. DO NOT use the "linked PR" feature]
• User Test Scripts: [when there are user test scripts available link them here]

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By using the extension mechanisms provided by the COAR notify common library, produce a set of model objects to represent the PCI workflow within Invenio.

Both AnnouceReview and AnnounceEndorsement would have the following fields and interpretations:

• Object - a reference to the PCI review page
  • Cite-as - DOI here points to the recommendation overall, not the individual reviews
• Context - the Zenodo item being reviewed
• Item - omitted (PCI does not send this, and it is not needed)
• inReplyTo - optional, and not necessary in the unsolicited-review case

Acceptance Criteria

List the criteria which must be met for the issue to be considered complete

• Each notify message used by PCI has a corresponding model object with any custom constraints and APIs