Completely remove old non-structured errors and migrate existing ones.

app/models/code_ocean/error.rb

@@ -1,19 +0,0 @@
-module CodeOcean
-  class Error < ApplicationRecord
-    belongs_to :execution_environment
-
-    scope :for_execution_environment, ->(execution_environment) { where(execution_environment_id: execution_environment.id) }
-    scope :grouped_by_message, -> { select('MAX(created_at) AS created_at, MAX(id) AS id, message, COUNT(id) AS count').group(:message).order('count DESC') }
-
-    validates :execution_environment_id, presence: true
-    validates :message, presence: true
-
-    def self.nested_resource?
-      true
-    end
-
-    def to_s
-      id.to_s
-    end
-  end
-end