Fix DST drift in occurrence generation

- Occurrence.generate_dates: use ChaosCalendar::occurrences_for_timezone
  with Time.zone.tzinfo.identifier — occurrences now keep wall-clock
  time across DST boundaries (19:00 stays 19:00 in summer and winter);
  requires chaoscalendar gem with occurrences_for_timezone support
  (Gemfile.lock bumped accordingly)
- Occurrence.find_in_range: joins(:event) inner join excludes occurrences
  whose event no longer exists (107k orphaned rows from the pre-revival
  calendar era were purged from the test DB); includes(:node) retained
  for eager loading; column references qualified with table name

1 files changed, 7 insertions, 5 deletions

diff --git a/app/models/occurrence.rb b/app/models/occurrence.rb
index 777be24..41ef4cb 100644
--- a/app/models/occurrence.rb
+++ b/app/models/occurrence.rb
@@ -10,9 +10,10 @@ class Occurrence < ApplicationRecord
   # Class Methods
   
   def self.find_in_range start_time, end_time
-    includes(:node)
-      .where("start_time > ? AND end_time < ?", start_time, end_time)
-      .order("start_time")
+    joins(:event)
+      .includes(:node)
+      .where("occurrences.start_time > ? AND occurrences.end_time < ?", start_time, end_time)
+      .order("occurrences.start_time")
   end
 
   def self.find_next
@@ -48,10 +49,11 @@ class Occurrence < ApplicationRecord
   # Return value is always an array of Time objects.
   def self.generate_dates event
     if event.rrule && !event.rrule.empty?
-      ChaosCalendar::occurrences( 
+      ChaosCalendar::occurrences_for_timezone( 
         event.start_time, 
         (Time.now + 5.years), 
-        event.rrule
+        event.rrule,
+        Time.zone.tzinfo.identifier
       )
     else
       [event.start_time]