User context manager

[EstAK]

Features

• Users managed through a UserManager
• User context manager to "safely" run commands on the behalf of a user
• Usage example : scala_container.py

Motivation

Instead of trusting the user to correctly scope where a user should be enable : encapsulate it. No need to use constructs like anymore :

def foo_builder():
    builder = PartialDockerBuilder()
    builder.root ()
    # some stuff
    builder.user()

now, you can use

def foo_builder(user_manager):
    builder = PartialDockerBuilder()
    builder.user_manager = user_manager
    with builder.as_root() as root_builder:
        # some stuff

at the end of the context manager you are ensured to return to the user that was used before entering it :

def foo_builder(user_manager): 
    builder = PartialDockerBuilder()
    builder.user_manager = user_manager
    with builder.as_user(username="user") as user_builder:
        # some stuff 
        with user_builder.as_root() as root_builder:
            # some stuff as root
       # some stuff as "user"again