Currently, there is no way to get all users who have starred/favorited a content. The only way to indirectly get this information via REST API is to call the "Find relationship from source to target" i.e, "/wiki/rest/api/relation/:relationName/from/:sourceType/:sourceKey/to/:targetType/:targetKey" endpoint where we need to add both user id and content id to check if there exists any 'favourite' relation.

We need to get the information on users who have starred a content for all content in a space for indexing purposes. So calling the above endpoint for each user and each content would be terribly expensive.

We request the team to either enrich the content metadata with the starred information or add the 'favourite' relation to the "Find source entities related to a target entity" i.e, "/wiki/rest/api/relation/{relationName}/to/{targetType}/{targetKey}/from/{sourceType}" endpoint or maybe add a new endpoint for it.