[Opensim-dev] Shaping the user services

[Melanie]

After breaking my head over this for a few weeks, I believe I have 
figured out how to do this in a sane way.

The fallacy was to assume that the login server and the user server 
would be one entity. That makes things overcomplicated and breaks 
the architecture all over the place.

Now, here is what I have come up with:

User Server:
- Resolve name to key queries
- Resolve key to name queries
- Provide avatar picker lists
- Manage home region data

Authentication server
- Create and manage authentication handles (string) and session keys 
(UUID)
- Check passwords or other forms of authentication

Login server
- Provide the interface for the Linden viewer to log into a grid. 
Uses the services above, but doesn't contain them.

Presence server
- Manages last position data
- Keeps list of logged in avatars and their locations

Alongside with this, a new database is needed. This will not be an 
upgrade path, but a parallel development with a migration tool.

Profile information has no place in this architecture and will be 
handled exclusively by the profiles module.

The user table will specifically be designed to accommodate 
additional fields and allow getting/setting of such fields.

With all user data, a scope identifier will be passed. This will be 
UUID.Zero in the most common case (Standalone or single grid) but 
will allow sharing of server processes between multiple logical grids.

Comments are welcome.

Melanie