get_related_resources() calls user_can_read_graph() multiple times for same graphs, huge slowdown

[whatisgalen]

At this section of get_related_resources method (used by the resource_report API endpoint):

for relation in resource_relations["relations"]:
            relation = model_to_dict(relation)
            resourceid_to = relation["resourceinstanceidto"]
            resourceid_from = relation["resourceinstanceidfrom"]
            resourceinstanceto_graphid = relation["resourceinstanceto_graphid"]
            resourceinstancefrom_graphid = relation["resourceinstancefrom_graphid"]

            if (
                resourceid_to not in restricted_instances
                and resourceid_from not in restricted_instances
                and user_can_read_graph(user, resourceinstanceto_graphid)
                and user_can_read_graph(user, resourceinstancefrom_graphid)
            ):
            ...

the user_can_read_graph permissions method makes an ORM query every time it's called, even on relations shows graph we've already check. This can slow things down significantly, to the point where a single report takes up to 2 minutes to load. The slowdown is especially noticeable for resources with 50+ relations

[whatisgalen]

completed in #11458