Support provide initial data on query editor

[wilkerlucio]

Pathom now has a stronger notion of "initial data".

In this task I'll add a new input for this initial data, using the codemirror editor. This will also affect auto-complete, giving suggestions based on the user's initial input.

Stretch: support auto-complete for initial data based on known attributes in the system

• [x] Editor
• [x] Auto-complete using connection attributes
• [x] Support boundary interface in Pathom 2