FIX: allowes forcing timezone displayed in local-dates

Use case being you might want to always display a specific timezone, but still have the possibility to show the tooltip with various timezones.

plugins/discourse-local-dates/spec/integration/local_dates_spec.rb

@@ -0,0 +1,38 @@
+require 'rails_helper'
+
+RSpec.describe "Local Dates" do
+  before do
+    freeze_time
+  end
+
+  it "should work" do
+    post = Fabricate(:post, raw: <<~SQL)
+      [date=2018-05-08 time=22:00 format="L LTS" forceTimezone="UTC" timezones="Europe/Paris|America/Los_Angeles"]
+    SQL
+
+    cooked = post.cooked
+
+    expect(cooked).to include('class="discourse-local-date"')
+    expect(cooked).to include('data-date="2018-05-08"')
+    expect(cooked).to include('data-format="L LTS"')
+    expect(cooked).to include('data-force-timezone="UTC"')
+
+    expect(cooked).to include(
+      'data-timezones="Europe/Paris|America/Los_Angeles"'
+    )
+
+    expect(cooked).to include('05/08/2018 3:00:00 PM (America: Los Angeles)')
+    expect(cooked).to include('05/09/2018 12:00:00 AM (Europe: Paris)')
+  end
+
+  it 'requires the right attributes to convert to a local date' do
+    post = Fabricate(:post, raw: <<~SQL)
+      [date]
+    SQL
+
+    cooked = post.cooked
+
+    expect(post.cooked).to include("<p>[date]</p>")
+    expect(cooked).to_not include('data-force-timezone=')
+  end
+end