Supports talks without speakers

Admins may want to have discussions or any other general activity
that does not have any particular speaker. Thus, speaker validation
is removed.

Closes https://github.com/openSUSE/osem/issues/2520

app/models/event.rb

@@ -44,7 +44,6 @@ class Event < ApplicationRecord
   validates :abstract, presence: true
   validates :event_type, presence: true
   validates :program, presence: true
-  validates :speakers, presence: true
   validates :max_attendees, numericality: { only_integer: true, greater_than_or_equal_to: 1, allow_nil: true }
 
   validate :max_attendees_no_more_than_room_size

app/views/admin/events/_datatable_row.haml

@@ -24,11 +24,15 @@
         Unknown submitter
 
     %td
+      - if event.speakers.any?
         - event.speakers_ordered.each do |speaker|
           .speaker
             = link_to speaker.name, admin_user_path(speaker)
             - unless speaker.registrations.for_conference(event.conference)
               %span.label.label-danger Unregistered
+      - else
+        .small
+          No Speaker
 
     - if @program.languages.present?
       %td

app/views/admin/events/show.html.haml

@@ -69,9 +69,10 @@
               %span{ 'class' => [icon_for_todo(progress_status['registered']), 'fa-lg'] }
           %tr
             %td
-              - if @event.speakers.count == 1
+              - speakers_count = @event.speakers.count
+              - if speakers_count == 1
                 = link_to 'Fill out speaker\'s biography', edit_admin_user_path(@event.speakers.first)
-              - else
+              - elsif speakers_count > 1
                 Fill out speaker's biography:
                 = speaker_links(@event)
             %td{ 'class' => class_for_todo(progress_status['biographies']) }

app/views/admin/reports/_all_events.html.haml

@@ -27,10 +27,14 @@
           %td
             = link_to event.title, edit_admin_conference_program_event_path(@conference.short_title, event)
             %br
+            - if(event.speakers.any?)
               .small
                 (Presented by
                 = speaker_links(event)
                 )
+            - else
+              .small
+                (No speaker)
 
           - %w(registered biographies commercials subtitle difficulty_level).each do |info|
             %td{'data-order' => "#{progress_status[info]}"}

app/views/admin/reports/_events_without_commercials.html.haml

@@ -18,4 +18,8 @@
           %td= event.id
           %td= link_to event.title, edit_admin_conference_program_event_path(@conference.short_title, event)
           %td
+            - if(event.speakers.any?)
               = speaker_links(event)
+            - else
+              .small
+                (No speaker)

app/views/proposals/show.html.haml

@@ -27,6 +27,7 @@
   .row
     .col-md-3
       %h3
+      - if event.speakers.any?
         Presented by:
         - @speakers_ordered.each do |speaker|
           .speakerinfo

app/views/schedules/_event.html.haml

@@ -15,6 +15,7 @@
       %small
         = event.subtitle
     %h4
+      - if(event.speakers.any?)
         presented by #{event.speaker_names}
     %p
       = markdown(truncate(event.abstract, length: 400))