FIX: allows to query a username made of integers (#25815)

If a user had `123456789` as username, it could be passed to the query as a number and the query would fail as it expects a string.

Also applies the same fix to groups.

plugins/chat/spec/queries/chat/users_from_usernames_and_groups_query_spec.rb

@@ -15,6 +15,12 @@ describe Chat::UsersFromUsernamesAndGroupsQuery do
       result = described_class.call(usernames: [user1.username, user4.username], groups: [])
       expect(result).to contain_exactly(user1, user4)
     end
+
+    it "works with a number" do
+      user = Fabricate(:user, username: 12_345_678)
+      result = described_class.call(usernames: [12_345_678], groups: [])
+      expect(result).to contain_exactly(user)
+    end
   end
 
   context "when searching by groups" do
@@ -22,6 +28,12 @@ describe Chat::UsersFromUsernamesAndGroupsQuery do
       result = described_class.call(usernames: [], groups: [group1.name])
       expect(result).to contain_exactly(user1, user2)
     end
+
+    it "works with a number" do
+      group = Fabricate(:public_group, users: [user1, user2], name: 12_345_678)
+      result = described_class.call(usernames: [], groups: [12_345_678])
+      expect(result).to contain_exactly(user1, user2)
+    end
   end
 
   context "when searching by both usernames and groups" do