[web] fetch token users in a single db query per access mode (#26078)

* [web] skip db query when getting empty list of users

* [web] fetch token users in a single db query per access mode

GitOrigin-RevId: fa5d9edcb761bd5d5e5ea07d137a5a86efdbdd5c

services/web/app/src/Features/User/UserGetter.js

@@ -269,6 +269,7 @@ const UserGetter = {
   getUsers(query, projection, callback) {
     try {
       query = normalizeMultiQuery(query)
+      if (query?._id?.$in?.length === 0) return callback(null, []) // shortcut for getUsers([])
       db.users.find(query, { projection }).toArray(callback)
     } catch (err) {
       callback(err)

services/web/test/unit/src/User/UserGetterTests.js

@@ -119,6 +119,17 @@ describe('UserGetter', function () {
       })
     })
 
+    it('should not call mongo with empty list', function (done) {
+      const query = []
+      const projection = { email: 1 }
+      this.UserGetter.getUsers(query, projection, (error, users) => {
+        expect(error).to.not.exist
+        expect(users).to.deep.equal([])
+        expect(this.find).to.not.have.been.called
+        done()
+      })
+    })
+
     it('should not allow null query', function (done) {
       this.UserGetter.getUser(null, {}, error => {
         error.should.exist