Formalize DoD requirements on Interface

[CFBaptista]

Formalize the non-functional requirements on Interface for the version 1.0 release of wflow in the DoD.

Tasks

• [x] Propose non-functional requirements in DoD
• [x] Decide with team on functional and non-functional requirements to keep
• [x] Update description of functional and non-functional requirements in the DoD
• [x] Verify correct level of specificity with @deltamarnix
• [x] Process review comments of @deltamarnix