Previously to check if hibernated room was old enough we had to fetch info
about all rooms from database. Now we repurpose created_at field in sql
to store that info, that allow us to have more efficient query just for it.
How to update an existing database:
ALTER TABLE vcard_search DROP CONSTRAINT vcard_search_pkey;
ALTER TABLE vcard_search ADD PRIMARY KEY (server_host, lusername);
Note that support for older specification is completely dropped,
i.e. no backward compatibility is provided since the XEPs are
still very experimental and being changed drastically
Accordingly, Mnesia/SQL/Riak table 'carboncopy' is not used anymore
and can be safely removed.
As a consequence, the commit deprecates the following options of
mod_carboncopy:
- ram_db_type
- use_cache
- cache_size
- cache_missed
- cache_life_time
Fixes#2663
