Strip any pre-existing <x/> tags which have an <item/> child with a
'jid' attribute from MUC MAM messages. This way, if such a tag exists,
clients can be sure it was added by mod_mam.
If a stream management session times out for a user who appears to be
using MAM, drop any unacknowledged messages rather than resending or
bouncing them. This avoids duplicates or bogus error messages.
However, this is only done if the new mod_mam option "assume_mam_usage"
is set to 'if_enabled' or 'on_request'. In the former case, a user is
assumed to be using MAM if archiving is enabled for his account. In the
latter case, MAM usage is assumed only if archiving was explicitly
requested by the client, or if archiving was enabled by means of
mod_mam's "request_activates_archiving" option.
Sort the messages retrieved from an Mnesia archive before selecting the
subset limited by the <max/> value. This makes sure the desired subset
of messages is sent to the client.
If the client doesn't specify a maximum number of messages to retrieve
per page, set a limit of 50 messages. If the client specifies a limit
larger than 250, cap the number to 250 messages.
These limits aren't enforced for MAM v0.2 requests though, as that
version of the XEP doesn't require clients to support RSM. The newer
revisions say that "a server MAY place a reasonable limit on how many
stanzas may be pushed to a client in one request. Whether or not the
client query included a <set/> element, the server MAY simply return its
limited results, modifying the <set/> element it returns appropriately."
If an <index/> is specified in the MAM request, reject the request
rather than ignoring the desired index and returning wrong results.
XEP-0059 says that the server "MAY return a <feature-not-implemented/>
error."
