Add icalendar, token

Gemfile

 # Error reporting
 gem 'sentry-raven'
 
+# Calendar support
+gem 'icalendar'
+
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platform: :mri

Gemfile.lock

     i18n (0.8.1)
     i18n_generators (2.1.1)
       rails (>= 3.0.0)
+    icalendar (2.4.1)
     jbuilder (2.6.3)
       activesupport (>= 3.0.0, < 5.2)
       multi_json (~> 1.2)
   font-awesome-sass
   haml
   i18n_generators
+  icalendar
   jbuilder (~> 2.5)
   jquery-rails
   listen (~> 3.0.5)

app/models/person.rb

   #   @return [String]
   #     the person's email address.
   #
+  # @!attribute calendar_token
+  #   @return [String]
+  #     the calendar token that can be used to open this Person's events as an
+  #     ICAL file.
+  #
   # @!attribute is_admin
   #   @return [Boolean]
   #     whether or not the person has administrative rights.
     dependent: :destroy
   has_many :groups, through: :members
   has_many :activities, through: :participants
+  has_secure_token :calendar_token
 
   validates :email, uniqueness: true
   validates :first_name, presence: true

db/migrate/20180904162042_add_calendar_token_to_people.rb

+class AddCalendarTokenToPeople < ActiveRecord::Migration[5.0]
+  def change
+    add_column :people, :calendar_token, :string
+    add_index :people, :calendar_token, unique: true
+  end
+end

db/migrate/20180904163645_generate_calendar_tokens.rb

+class GenerateCalendarTokens < ActiveRecord::Migration[5.0]
+  def up
+    Person.all.each do |p|
+      p.regenerate_calendar_token
+    end
+  end
+
+  def down
+  end
+end

db/schema.rb

 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180206181016) do
+ActiveRecord::Schema.define(version: 20180904163645) do
 
   create_table "activities", force: :cascade do |t|
     t.string   "name"
     t.datetime "created_at",                              null: false
     t.datetime "updated_at",                              null: false
     t.boolean  "send_attendance_reminder", default: true
+    t.string   "calendar_token"
+    t.index ["calendar_token"], name: "index_people_on_calendar_token", unique: true
     t.index ["email"], name: "index_people_on_email", unique: true
   end