add method to retrieve thread by external_thread_id or recipient_name
add ThreadMessageLookup core
no more MessageLookup so, delegate lookup and thread management outside scope of Message.create method
when creating new thread, initialize lookups related object
external_thread_id and from_ in NewMessage parameter
lookups and thread create/update logic start appear in UserMessageDelivery
set Message.date value
remove __init_lookup logic, not good this way
remove ThreadRecipientLookup in lookups
add Message.from_ attribute and build a sequence for lookup on mail message
use of lookup_sequence, prepare for lookup init when thread created
_lookups is a dict configuration
some debug for lookup logic
add a timeit decorator to trace import method during message processing for an user
init lookups a minima after thread creation and update