Use cache for authentication backends

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`.

1 files changed, 6 insertions, 41 deletions

diff --git a/src/ejabberd_auth_pam.erl b/src/ejabberd_auth_pam.erl
index 9d2fc819..f865f36f 100644
--- a/src/ejabberd_auth_pam.erl
+++ b/src/ejabberd_auth_pam.erl
@@ -30,14 +30,8 @@
 
 -behaviour(ejabberd_auth).
 
--export([start/1, stop/1, set_password/3, check_password/4,
-	 check_password/6, try_register/3,
-	 dirty_get_registered_users/0, get_vh_registered_users/1,
-	 get_vh_registered_users/2,
-	 get_vh_registered_users_number/1,
-	 get_vh_registered_users_number/2, get_password/2,
-	 get_password_s/2, is_user_exists/2, remove_user/2,
-	 remove_user/3, store_type/0, plain_password_required/0,
+-export([start/1, stop/1, check_password/4,
+	 is_user_exists/2, store_type/1, plain_password_required/1,
 	 opt_type/1]).
 
 start(_Host) ->
@@ -46,13 +40,6 @@ start(_Host) ->
 stop(_Host) ->
     ok.
 
-set_password(_User, _Server, _Password) ->
-    {error, not_allowed}.
-
-check_password(User, AuthzId, Server, Password, _Digest,
-	       _DigestGen) ->
-    check_password(User, AuthzId, Server, Password).
-
 check_password(User, AuthzId, Host, Password) ->
     if AuthzId /= <<>> andalso AuthzId /= User ->
         false;
@@ -70,25 +57,6 @@ check_password(User, AuthzId, Host, Password) ->
         end
     end.
 
-try_register(_User, _Server, _Password) ->
-    {error, not_allowed}.
-
-dirty_get_registered_users() -> [].
-
-get_vh_registered_users(_Host) -> [].
-
-get_vh_registered_users(_Host, _) -> [].
-
-get_vh_registered_users_number(_Host) -> 0.
-
-get_vh_registered_users_number(_Host, _) -> 0.
-
-get_password(_User, _Server) -> false.
-
-get_password_s(_User, _Server) -> <<"">>.
-
-%% @spec (User, Server) -> true | false | {error, Error}
-%% TODO: Improve this function to return an error instead of 'false' when connection to PAM failed
 is_user_exists(User, Host) ->
     Service = get_pam_service(Host),
     UserInfo = case get_pam_userinfotype(Host) of
@@ -97,16 +65,13 @@ is_user_exists(User, Host) ->
 	       end,
     case catch epam:acct_mgmt(Service, UserInfo) of
       true -> true;
-      _ -> false
+      false -> false;
+      _Err -> {error, db_failure}
     end.
 
-remove_user(_User, _Server) -> {error, not_allowed}.
-
-remove_user(_User, _Server, _Password) -> not_allowed.
-
-plain_password_required() -> true.
+plain_password_required(_) -> true.
 
-store_type() -> external.
+store_type(_) -> external.
 
 %%====================================================================
 %% Internal functions