Feature: Access Control Enchancements

[arg3t]

Description

This PR re-implements the access control mechanism such that:

• Each note has a privilege vector associated with it
• This vector is propagated into relations
• Each entity is an item in the vector. If a note requires access to entity A then that index of the privilege vector is set to 1, otherwise 0
• A user's access level is also a vector, access into a note is decided by strictly comparing each item in the vector
• BREAKING Now, a maximum of 2048 entities are supported. This number can be increased in the future in exchange for a small hit on performance.
• BREAKING After migrating, users need to run pipenv run python manage.py calculate_acvecs in order to properly initialize the access control vectors. Otherwise they won't work

Fixes #11 & #1

Affected Components

Please indicate which parts of the application this PR concerns. For example, you can include any of the following:

• Frontend
• Backend

Type of Change

• Bug fix
• New feature
• Breaking change

Checklist

• I have performed a self-review of my own code.
• I have commented my code where necessary.
• I have made corresponding changes to the documentation.
• My changes do not produce any new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• Any dependent changes have been merged and published.