Merge pull request #230 from openHPI/fix_download

Specify `ExternalUser` as class for `user` in `RemoteEvaluationMapping`

db/migrate/20181126163428_add_user_type_to_remote_evaluation_mappings.rb

@@ -0,0 +1,8 @@
+class AddUserTypeToRemoteEvaluationMappings < ActiveRecord::Migration[5.2]
+  def change
+    add_column :remote_evaluation_mappings, :user_type, :string
+    # Update all existing records and set user_type to `ExternalUser` (safe way to prevent any function loss).
+    # We are not using a default value here on intend to be in line with the other `user_type` columns
+    RemoteEvaluationMapping.update_all(user_type: 'ExternalUser')
+  end
+end