feat: #11240, only show relevant users in flags assignee list

for user flags-> admins + all users who have `admin:users` privilege
for post flags -> admins + global mods + moderators of the category the post is in
refactor getModeratorUids function so it can be used for different privileges

src/privileges/helpers.js

@@ -6,6 +6,7 @@ const validator = require('validator');
 
 const groups = require('../groups');
 const user = require('../user');
+const categories = require('../categories');
 const plugins = require('../plugins');
 const translator = require('../translator');
 
@@ -189,4 +190,38 @@ helpers.userOrGroupPrivileges = async function (cid, uidOrGroup, privilegeList)
 	return _.zipObject(privilegeList, isMembers);
 };
 
+helpers.getUidsWithPrivilege = async (cids, privilege) => {
+	const disabled = (await categories.getCategoriesFields(cids, ['disabled'])).map(obj => obj.disabled);
+
+	const groupNames = cids.reduce((memo, cid) => {
+		memo.push(`cid:${cid}:privileges:${privilege}`);
+		memo.push(`cid:${cid}:privileges:groups:${privilege}`);
+		return memo;
+	}, []);
+
+	const memberSets = await groups.getMembersOfGroups(groupNames);
+	// Every other set is actually a list of user groups, not uids, so convert those to members
+	const sets = memberSets.reduce((memo, set, idx) => {
+		if (idx % 2) {
+			memo.groupNames.push(set);
+		} else {
+			memo.uids.push(set);
+		}
+
+		return memo;
+	}, { groupNames: [], uids: [] });
+
+	const uniqGroups = _.uniq(_.flatten(sets.groupNames));
+	const groupUids = await groups.getMembersOfGroups(uniqGroups);
+	const map = _.zipObject(uniqGroups, groupUids);
+	const uidsByCid = cids.map((cid, index) => {
+		if (disabled[index]) {
+			return [];
+		}
+
+		return _.uniq(sets.uids[index].concat(_.flatten(sets.groupNames[index].map(g => map[g]))));
+	});
+	return uidsByCid;
+};
+
 require('../promisify')(helpers);