Fix csv upload (#13835)

app/models/import.rb

@@ -17,7 +17,7 @@
 #
 
 class Import < ApplicationRecord
-  FILE_TYPES = %w(text/plain text/csv).freeze
+  FILE_TYPES = %w(text/plain text/csv application/csv).freeze
   MODES = %i(merge overwrite).freeze
 
   self.inheritance_column = false

config/initializers/paperclip.rb

@@ -111,3 +111,5 @@ else
     url: ENV.fetch('PAPERCLIP_ROOT_URL', '/system') + '/:prefix_url:class/:attachment/:id_partition/:style/:filename',
   )
 end
+
+Paperclip.options[:content_type_mappings] = { csv: Import::FILE_TYPES }