studio: mock api

[peterpeterparker]

To ease the local development, as long as we don't have a staging api (#274), mock the api

[nmattia]

@peterpeterparker which API is that?

[peterpeterparker]

@nmattia our api (user(name), presentation, etc.)

[peterpeterparker]

P.S.: it will ease my development (no need to stash authentication anymore) and also will make easier for contributors to run studio locally