[Galene] Heads up: group description format changes

[Juliusz Chroboczek <jch@irif.fr>]

I'm almost ready to merge the "api" branch into master.  The group
description format is going to change, so here's a description of the
changes.

I haven't merged into master yet, so feel free to comment and criticise.


# Backwards compatibility is mostly preserved

Galene will continue reading old-format group descriptions, and
transparently convert them to the new format.  There are, however, some
minor details that will not be converted automatically:

  * "allow-anonymous" is ignored

    It is the default behaviour now.

  * It is no longer possible to have multiple users with the same username

    You used to be able to say

        "op": [{"username":"jch","password":"verysecret"}],
        "present": [{"username":"jch","password":"somewhatsecret"}],

    and Galene would choose the right permissions based on the password.  This
    is no longer possible, there can be only one user with a given username.

  * The config.json file has changed

    The "admin" field in the config.json file is ignored.  There is a new
    field "users".


# The new format

The following fields are obsolete:

  - op, presenter, other;
  - allow-anonymous.

In addition, The field "allow-subgroups" has been renamed to "auto-subgroups".

Instead of the three fields for users, there is just a single dictionary
called "users".  So instead of saying

    "op": [{"username":"jch","password":"verysecret"}],
    "present": [{"username":"john","password":"somewhatsecret"}],

you now say

    "users": {
        "jch": {"permissions": "op", "password": "verysecret"},
        "john": {"permissions": "present", "password": "somewhatsecret"}
    }

In order to convert fields with no username (wildcards), there is a new
field "fallback-users".  However, its use is not recommended -- tokens are
the new way of providing password-less access.


# Changes to the configuration file

The same changes have been applied to "config.json": the field "admin" is
obsolete, you should now say something like

    "users": {
        "jch": {"permissions": "admin", "password": "verysecret"}
    ]

Unlike the group files, which preserve compatibility, the config.json file
does not -- you'll need to modify it manually.


-- Juliusz