[GOFLOW-30] Support for a UI dag builder

[giorgiozoppi]

Goflow DAG builder: Provide a UI DAG builder

Goal

The goal of this story is to make it easier to build dag from a data engineer prospective. A data engineer shall not be able to be proficent in Go and basically we want to provide an UI where he/she is able to draw a dag. We want to leverage the https://github.com/AlexImb/vue-dag library to obtain that scope.

Requirement of the story:

Functional requirement

As end user i want to:

1. Create a graph by the UI.
2. Select for each node the workflow code and edit that.
3. Save/Resume the workflow

Tecnical requirements:

So the scope of this story is: 1 . Create a UI that is able to draw/save a graph and schedule its execution. 2.. Provide a REST api that is able to submit a transpiled graph.