made event attendees a multiselect instead of autocomplete

config/core.entity_form_display.oc_event.train_the_trainer.default.yml

@@ -4,13 +4,17 @@ status: true
 dependencies:
   config:
     - opencase_entities.oc_event_type.train_the_trainer
-  module:
-    - datetime
 id: oc_event.train_the_trainer.default
 targetEntityType: oc_event
 bundle: train_the_trainer
 mode: default
 content:
+  attendees:
+    type: options_select
+    weight: 2
+    region: content
+    settings: {  }
+    third_party_settings: {  }
   name:
     type: string_textfield
     weight: 0
@@ -26,4 +30,7 @@ content:
     settings:
       display_label: true
     third_party_settings: {  }
-hidden: {  }
+hidden:
+  activity_date_time: true
+  description: true
+  user_id: true