FIX: topic timer offset applied two times

timezone offset was calculated and sent from browser to server, it would be applied on utc time generated from '2013-11-22 5:00' format for example and then sent back to browser which would display it thinking it's UTC time using `moment(utc time)` when it's in fact an UTC time we have offseted with the initial user timezone.

This is impossible to automatically test in the current app state. Easiest reproduction is in live browser after setting your timezone to `America/New_York`, when setting a topic timer to later_today, after save, the time under the topic should be off to something roughly equal +1/-1  hour to your timezone offset.

app/assets/javascripts/discourse/models/topic-timer.js.es6

@@ -6,8 +6,7 @@ const TopicTimer = RestModel.extend({});
 TopicTimer.reopenClass({
   updateStatus(topicId, time, basedOnLastPost, statusType, categoryId) {
     let data = {
-      time: time,
+      time,
-      timezone_offset: (new Date().getTimezoneOffset()),
       status_type: statusType
     };
 

app/controllers/topics_controller.rb

@@ -287,7 +287,7 @@ class TopicsController < ApplicationController
   end
 
   def timer
-    params.permit(:time, :timezone_offset, :based_on_last_post, :category_id)
+    params.permit(:time, :based_on_last_post, :category_id)
     params.require(:status_type)
 
     status_type =
@@ -302,7 +302,6 @@ class TopicsController < ApplicationController
 
     options = {
       by_user: current_user,
-      timezone_offset: params[:timezone_offset]&.to_i,
       based_on_last_post: params[:based_on_last_post]
     }
 

app/models/topic.rb

@@ -1032,10 +1032,9 @@ SQL
   #  * `nil` to delete the topic's status update.
   # Options:
   #  * by_user: User who is setting the topic's status update.
-  #  * timezone_offset: (Integer) offset from UTC in minutes of the given argument.
   #  * based_on_last_post: True if time should be based on timestamp of the last post.
   #  * category_id: Category that the update will apply to.
-  def set_or_create_timer(status_type, time, by_user: nil, timezone_offset: 0, based_on_last_post: false, category_id: SiteSetting.uncategorized_category_id)
+  def set_or_create_timer(status_type, time, by_user: nil, based_on_last_post: false, category_id: SiteSetting.uncategorized_category_id)
     return delete_topic_timer(status_type, by_user: by_user) if time.blank?
 
     public_topic_timer = !!TopicTimer.public_types[status_type]
@@ -1067,7 +1066,6 @@ SQL
       if is_timestamp && time.include?("-") && timestamp = utc.parse(time)
         # a timestamp in client's time zone, like "2015-5-27 12:00"
         topic_timer.execute_at = timestamp
-        topic_timer.execute_at += timezone_offset * 60 if timezone_offset
         topic_timer.errors.add(:execute_at, :invalid) if timestamp < now
       else
         num_hours = time.to_f

spec/models/topic_spec.rb

@@ -1236,24 +1236,12 @@ describe Topic do
       expect(topic.topic_timers.first.execute_at).to eq(3.days.from_now)
     end
 
-    it 'can take a number of hours as an integer, with timezone offset' do
-      freeze_time now
-      topic.set_or_create_timer(TopicTimer.types[:close], 72, by_user: admin, timezone_offset: 240)
-      expect(topic.topic_timers.first.execute_at).to eq(3.days.from_now)
-    end
-
     it 'can take a number of hours as a string' do
       freeze_time now
       topic.set_or_create_timer(TopicTimer.types[:close], '18', by_user: admin)
       expect(topic.topic_timers.first.execute_at).to eq(18.hours.from_now)
     end
 
-    it 'can take a number of hours as a string, with timezone offset' do
-      freeze_time now
-      topic.set_or_create_timer(TopicTimer.types[:close], '18', by_user: admin, timezone_offset: 240)
-      expect(topic.topic_timers.first.execute_at).to eq(18.hours.from_now)
-    end
-
     it 'can take a number of hours as a string and can handle based on last post' do
       freeze_time now
       topic.set_or_create_timer(TopicTimer.types[:close], '18', by_user: admin, based_on_last_post: true)
@@ -1266,12 +1254,6 @@ describe Topic do
       expect(topic.topic_timers.first.execute_at).to eq(Time.zone.local(2013, 11, 22, 5, 0))
     end
 
-    it "can take a timestamp for a future time, with timezone offset" do
-      freeze_time now
-      topic.set_or_create_timer(TopicTimer.types[:close], '2013-11-22 5:00', by_user: admin, timezone_offset: 240)
-      expect(topic.topic_timers.first.execute_at).to eq(Time.zone.local(2013, 11, 22, 9, 0))
-    end
-
     it "sets a validation error when given a timestamp in the past" do
       freeze_time now
       topic.set_or_create_timer(TopicTimer.types[:close], '2013-11-19 5:00', by_user: admin)