The major goal is to simplify certificate management in ejabberd.
Currently it requires some effort from a user to configure certficates,
especially in the situation where a lot of virtual domains are hosted.
The task is splitted in several sub-tasks:
* Implement basic certificate validator. The validator should check all
configured certificates for existence, validity, duration and so on. The
validator should not perform any actions in the case of errors except
logging an error message. This is actually implemented by this commit.
* All certificates should be configured inside a single section (something
like 'certfiles') where ejabberd should parse them, check the full-chain,
find the corresponding private keys and, if needed, resort chains and
split the certficates into separate files for easy to use by fast_tls.
* Options like 'domain_certfile', 'c2s_certfile' or 's2s_certfile' should
probably be deprecated, since the process of matching certificates with the
corresponding virtual hosts should be done automatically and these options
only introduce configuration errors without any meaningful purpose.
The commit introduces the following API incompatibilities:
In ejabberd_auth.erl:
* dirty_get_registered_users/0 is renamed to get_users/0
* get_vh_registered_users/1 is renamed to get_users/1
* get_vh_registered_users/2 is renamed to get_users/2
* get_vh_registered_users_number/1 is renamed to count_users/1
* get_vh_registered_users_number/2 is renamed to count_users/2
In ejabberd_auth callbacks
* plain_password_required/0 is replaced by plain_password_required/1
where the argument is a virtual host
* store_type/0 is replaced by store_type/1 where the argument is
a virtual host
* set_password/3 is now an optional callback
* remove_user/3 callback is no longer needed
* remove_user/2 now should return `ok | {error, atom()}`
* is_user_exists/2 now must only be implemented for backends
with `external` store type
* check_password/6 is no longer needed
* check_password/4 now must only be implemented for backends
with `external` store type
* try_register/3 is now an optional callback and should return
`ok | {error, atom()}`
* dirty_get_registered_users/0 is no longer needed
* get_vh_registered_users/1 is no longer needed
* get_vh_registered_users/2 is renamed to get_users/2
* get_vh_registered_users_number/1 is no longer needed
* get_vh_registered_users_number/2 is renamed to count_users/2
* get_password_s/2 is no longer needed
* get_password/2 now must only be implemented for backends with
`plain` or `scram` store type
Additionally, the commit introduces two new callbacks:
* use_cache/1 where the argument is a virtual host
* cache_nodes/1 where the argument is a virtual host
New options are also introduced: `auth_use_cache`, `auth_cache_missed`,
`auth_cache_life_time` and `auth_cache_size`.
