Allow scheduling volunteers for sessions.

Also fix a small bug for admin registrations edit.

app/models/event.rb

@@ -18,6 +18,9 @@ class Event < ApplicationRecord
   has_one :submitter_event_user, -> { where(event_role: 'submitter') }, class_name: 'EventUser'
   has_one  :submitter, through: :submitter_event_user, source: :user
 
+  has_many :volunteer_event_users, -> { where(event_role: 'volunteer') }, class_name: 'EventUser'
+  has_many :volunteers, through: :volunteer_event_users, source: :user
+
   has_many :votes, dependent: :destroy
   has_many :voters, through: :votes, source: :user
   has_many :commercials, as: :commercialable, dependent: :destroy

app/models/event_user.rb

@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 class EventUser < ApplicationRecord
-  # TODO: Do we need these roles?
-  ROLES = [%w[Speaker speaker], %w[Submitter submitter], %w[Moderator moderator]]
+  ROLES = [%w[Speaker speaker], %w[Submitter submitter], %w[Moderator moderator],
+            %w[Volunteer volunteer]]
 
   belongs_to :event, touch: true
   belongs_to :user

app/models/user.rb

@@ -256,6 +256,12 @@ class User < ApplicationRecord
     result
   end
 
+  # TODO: Use a real authorization in the right place....
+  def manages_volunteers?(conference)
+    organizer_roles = get_roles['organizer']
+  organizer_roles&.include?(conference.short_title) # TODO or Volunteer Coorinator.
+  end
+
   def registered
     registrations = self.registrations
     if registrations.count == 0
@@ -290,6 +296,11 @@ class User < ApplicationRecord
     proposals(conference).count
   end
 
+  def volunteer_duties(conference)
+    events.where(program_id: conference.program.id, 'event_users.event_role': 'volunteer')
+  end
+
+
   def self.empty?
     User.count == 1 && User.first.email == 'deleted@localhost.osem'
   end