add Message.delete!(id:) (#15)

lib/outboxer/message.rb

@@ -79,6 +79,20 @@ def failed!(id:, exception:)
       end
     end
 
+    def delete!(id:)
+      ActiveRecord::Base.connection_pool.with_connection do
+        ActiveRecord::Base.transaction do
+          outboxer_message = Models::Message.includes(exceptions: :frames).find_by!(id: id)
+
+          outboxer_message.exceptions.each { |exception| exception.frames.destroy_all }
+          outboxer_message.exceptions.destroy_all
+          outboxer_message.destroy
+        end
+      end
+
+      { 'id' => id }
+    end
+
     def republish!(id:)
       ActiveRecord::Base.connection_pool.with_connection do
         outboxer_message = Models::Message.lock.find_by!(id: id)

spec/lib/outboxer/message/delete_spec.rb

@@ -0,0 +1,21 @@
+require 'spec_helper'
+
+module Outboxer
+  RSpec.describe Message do
+    describe '.delete!' do
+      let!(:message) { create(:outboxer_message, :failed) }
+      let!(:exception) { create(:outboxer_exception, message: message) }
+      let!(:frame) { create(:outboxer_frame, exception: exception) }
+
+      let!(:result) { Message.delete!(id: message.id) }
+
+      it 'deletes the message' do
+        expect(Models::Message).not_to exist(message.id)
+      end
+
+      it 'returns the message id' do
+        expect(result['id']).to eq(message.id)
+      end
+    end
+  end
+end