Show the precise ending time unless it's midnight

The reason why we were displaying the ending date as "one second before
the actual ending" was that, when seeing that a phase ends at a date
like "2000-12-31 00:00", we might end up thinking that the phase will
finished at the midnight between December 31st and January the 1st,
while it actually ends at the midnight between December the 30th and
December the 31st.

This is particularly important because we use a date field to select the
date of a phase and if select December the 31st, it will be stored in
the database as "2000-12-31 00:00". So, instead, in this case we display
"2000-12-30 23:59", which is less confusing.

But now we're going to add support for setting a time on polls, which
means a certain poll might end at 15:30. In this case, displaying that
it ends at 15:29 doesn't make much sense.

app/components/admin/duration_component.rb

@@ -16,6 +16,10 @@ class Admin::DurationComponent < ApplicationComponent
     end
 
     def end_time
-      durable.ends_at - 1.second if durable.ends_at.present?
+      if durable.ends_at.present? && durable.ends_at == durable.ends_at.beginning_of_day
+        durable.ends_at - 1.second
+      else
+        durable.ends_at
+      end
     end
 end

spec/components/admin/duration_component_spec.rb

@@ -9,9 +9,20 @@ describe Admin::DurationComponent do
 
     render_inline Admin::DurationComponent.new(durable)
 
-    expect(page.text).to eq "2015-08-01 12:00 - 2016-09-30 16:29"
+    expect(page.text).to eq "2015-08-01 12:00 - 2016-09-30 16:30"
     expect(page).to have_css "time", exact_text: "2015-08-01 12:00"
-    expect(page).to have_css "time", exact_text: "2016-09-30 16:29"
+    expect(page).to have_css "time", exact_text: "2016-09-30 16:30"
+  end
+
+  it "shows the moment before the end date when it ends at midnight" do
+    durable = double(
+      starts_at: Time.zone.local(2015, 8, 1, 12, 0, 0),
+      ends_at: Time.zone.local(2016, 9, 30, 00, 00, 00)
+    )
+
+    render_inline Admin::DurationComponent.new(durable)
+
+    expect(page.text).to eq "2015-08-01 12:00 - 2016-09-29 23:59"
   end
 
   it "shows the start date when no end date is defined" do
@@ -27,6 +38,6 @@ describe Admin::DurationComponent do
 
     render_inline Admin::DurationComponent.new(durable)
 
-    expect(page.text).to eq "- 2016-09-30 16:29"
+    expect(page.text).to eq "- 2016-09-30 16:30"
   end
 end