allow filtering item search results by a contributor's actor id and role

[stefanprobst]

some consumers of the sshoc marketplace api need to filter the /api/item-search response by a specific institutional affiliation, i.e. a specific contributor.

one example is the tools and services catalogue on the dariah.eu website (https://www.dariah.eu/tools-services/tools-and-services/), similar listings are in planning stage.

filtering item search results by a specific contributor's actor.id and role.code is currently rather cumbersome. how difficult would it be to add such filtering capabilities to /api/item-search?

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i am aware i can get items associated with an actor via /api/actors/:id?items=true, however this does not provide information about the actor's role, so it would require separate requests for each search result to figure out the role and use it for filtering.