Modify model to take multiple attachements

app/controllers/messages_controller.rb

@@ -37,7 +37,7 @@ def create
   def download_attachment
     raise 'No attachment present on this message' unless message.attachment.attached?
 
-    redirect_to message.attachment.blob.url(disposition: 'attachment'), allow_other_host: true
+    redirect_to message.attachment.first.blob.url(disposition: 'attachment'), allow_other_host: true
   end
 
   private
@@ -59,10 +59,10 @@ def message_params
     params.require(:message).permit(
       :sender_id,
       :claim_id,
-      :attachment,
       :body,
       :claim_action,
-      :written_reasons_submitted
+      :written_reasons_submitted,
+      attachment: []
     )
   end
 end

app/interfaces/api/entities/document.rb

@@ -9,19 +9,19 @@ class Document < BaseEntity
       private
 
       def attachment
-        object.is_a?(ActiveStorage::Attachment) ? object : object.attachment
+        object.is_a?(ActiveStorage::Attachment) ? object : object.attachment.first
       end
 
       def url
-        attachment.blob.url(disposition: 'attachment') if attachment.attached?
+        attachment.first.blob.url(disposition: 'attachment') if attachment.first.attached?
       end
 
       def file_name
-        attachment.filename if attachment.attached?
+        attachment.first.filename if attachment.first.attached?
       end
 
       def size
-        attachment.byte_size if attachment.attached?
+        attachment.first.byte_size if attachment.first.attached?
       end
     end
   end

app/models/message.rb

@@ -21,7 +21,7 @@ class Message < ApplicationRecord
 
   attr_accessor :claim_action, :written_reasons_submitted
 
-  has_one_attached :attachment
+  has_many_attached :attachment
 
   validates :attachment,
             size: { less_than: 20.megabytes },
@@ -51,7 +51,7 @@ class Message < ApplicationRecord
   scope :most_recent_last, -> { includes(:user_message_statuses).order(created_at: :asc) }
 
   after_create :generate_statuses, :process_claim_action, :process_written_reasons, :send_email_if_required
-  before_destroy -> { attachment.purge }
+  before_destroy -> { attachment.each(&:purge) }
 
   class << self
     def for(object)

app/presenters/message_presenter.rb

@@ -8,7 +8,7 @@ def sender_is_a?(klass)
   def body
     h.tag.div do
       h.concat(simple_format(message.body))
-      attachment_field if message.attachment.present?
+      attachment_field if message.attachment.first.present?
     end
   end
 
@@ -39,11 +39,11 @@ def download_file_link
   end
 
   def attachment_file_name
-    message.attachment.filename.to_s
+    message.attachment.first.filename.to_s
   end
 
   def attachment_file_size
-    h.number_to_human_size(message.attachment.byte_size)
+    h.number_to_human_size(message.attachment.first.byte_size)
   end
 
   def hide_author?