Django authentication with fine-grained access control

I am developing a Django web application with a suite of steel design tools for structural engineers. There will be a database table of inputs for each design tool, and each row of each table will correspond to a particular design condition to be "solved." The users may work solely or in groups. Each user needs to have ongoing access to his own work so that designs can be refined, copied and adapted, and so that reports can be created whenever convenient, usually at the end of a project when hard copy documentation will be needed. The database contents must then be available over any number of sessions occurring over periods measured in months or even years for a given design project.

When there is a group of users, typically all associated with a given design office, it will probably be acceptable for them all to have joint and mutual access to each other's work. The application supports routine engineering production activities, not innovative intellectual property work, and in-house privacy is not the norm in the industry anyway. However, the work absolutely must be shielded from prying eyes outside of the group. Ideally, each group would have one or more superusers authorized to police the membership of the group. Probably the main tool they would need would be the ability to remove a member from the group, discontinuing his access privileges. This would be a user group superuser and would not be the sa开发者_开发问答me as a superuser on the site side.

For convenient access, each row of each database table will be associated with a project number/project name pair that will be unique for a given company deploying a user or user group. A different company could easily choose to use a duplicate project number, and even could choose a duplicate project name, so discriminating exactly which database rows belong to a given user (or group) will probably have to be tracked in a separate related "ownership list" table for each user (or group).

It is anticipated (hoped) that, eventually, several hundred users (or user groups) associated with different (and often competing) companies will solve tens of thousands of design conditions for thousands of projects using these tools.

So, here are my questions:

First, is there any point in trying to salvage much of anything from the Django contrib.auth code? As I perceive it, contrib.auth is designed for authentication and access control that is suitable for the blogosphere and web journalism, but that doesn't support fine-grained control of access to "content."

Second, is there any available template, pattern, example, strategy or design advice I could apply to this problem?

django-authority: Documentation, code on GitHub