feat(rest): Rename User and introduce Account, UserProfile

User entity which was referenced in Project and issue is refactored into two entities. Account entity holds information like email, password and so whereas UserProfile holds information about the display aspect of the account and it is the one referenced in other entities.
feat(rest): Add validator for Account

Add sample validator for Account entity and a test to verify behaviour.
test(oauth): Add base class for integration tests

Base class provides methods to create bearer tokens to test authenticated scenarios.
refactor(domain): Rename model package to domain package
test(domain): Add account event handler test