Phase 1: standalone events, external_url on nodes

- Migration: node_id nullable on events and occurrences, add
  title/description/is_primary to events, external_url to nodes
- Existing events marked is_primary: true (were all 1:1 with nodes)
- Node: has_one :event -> has_many :events
- Event: belongs_to :node optional, validates title presence for
  standalone events, is_primary uniqueness scoped to node_id,
  display_title helper falling back through node title
- Occurrence: belongs_to :node optional, summary falls back to
  event.display_title
- nodes_helper: event_information uses events.first (interim; will
  be replaced in Phase 3 event UI)
- Tests: fix node.event -> node.events.first in event_test

1 files changed, 4 insertions, 5 deletions

diff --git a/app/models/occurrence.rb b/app/models/occurrence.rb
index 3baf447..143124f 100644
--- a/app/models/occurrence.rb
+++ b/app/models/occurrence.rb
@@ -1,13 +1,12 @@
-# TODO Make a gem out of the c wrapper
 require 'chaos_calendar'
 
 class Occurrence < ApplicationRecord
   
   # Associations
   
-  belongs_to :node
+  belongs_to :node,  optional: true
   belongs_to :event
-  
+
   # Class Methods
   
   def self.find_in_range start_time, end_time
@@ -64,7 +63,7 @@ class Occurrence < ApplicationRecord
   # Instance Methods
   
   def summary
-    node.head.title
+    node&.head&.title || event.display_title
   end
-  
+
 end