PR Description

A draft PR for proof of concept of workflow builder (Dashflow) for APIDash.
This contains a workflow canvas with sample nodes, control node having various control buttons on it including a add node button which creates a new node everytime on click in canvas.

• infinite grid canvas with pan, zoom features
• draggable and interconnectable nodes
• editable node details on one click
• creating new node on one click
• control node for canvaswide tasks

Screenshots

• Related GSoC application GSoC application for Workflow builder and Api testing suite #789

Checklist

• I have gone through the contributing guide
• I have updated my branch and synced it with project main branch before making this PR
• I am using the latest Flutter stable branch (run flutter upgrade and verify)
• I have run the tests (flutter test) and all tests are passing

Added/updated tests?

We encourage you to add relevant test cases.

• Yes
• No

OS on which you have developed and tested the feature?

• Windows
• macOS
• Linux