Handle reply to document

This is intended to work with an extension of crm_claim that allows to respond to the partner with a specific email wizard, that is not connected to the chatter.  To be more specific, in my usecase, we separate the chatter, that is used for internal communication between staff members, and an email response feature that is only used to communicate with the partner (to give the final answer, resolution of the incident).

When we send an email to the partner in this way, we also need to handle replies that we may receive from the partner (not a subscriber) and include them in the chatter.

Changing message_route() is the only way to get the reply, otherwise OpenERP fails with the following message:

    2014-07-24 13:35:44,921 7171 ERROR cmlid openerp.addons.fetchmail.fetchmail: Failed to process mail from imap server Hotline.
    Traceback (most recent call last):
      File "/path/to/odoo/addons/fetchmail/fetchmail.py", line 202, in fetch_mail
        context=context)
      File "/path/to/custom/mail_thread.py", line 49, in message_process
        thread_id, context)
      File "/path/to/odoo/addons/mail/mail_thread.py", line 699, in message_process
        
      File "/path/to/odoo/addons/mail/mail_thread.py", line 623, in message_route
        if not (thread_id and hasattr(model_pool, 'message_update') or hasattr(model_pool, 'message_new')):
    ValueError: No possible route found for incoming message from Mr Partner <mr.partner@mydomain.com> to Hotline <hotline@mycompany.com> (Message-Id <some.id@server.com>:). Create an appropriate mail.alias or force the destination model

To be more specific, my scenario is to have custom notification messages using email_template.  Please have a look at my implementation of ``mail_followers._notify()`` below (this is an excerpt):

    def _notify(self, cr, uid, msg_id, partners_to_notify=None, context=None):
        obj = self.pool.get(msg.model)
        claim = obj.browse(cr, uid, msg.res_id, context=context)
        context['document'] = claim

        tmpl_obj=self.pool.get('email.template')

        template = self.getClaimTemplate(claim.categ_id)
        if template is False:
            raise Exception("Could not find template for claim category %s" % claim.categ_id)

        if context.has_key('default_composition_mode'):
            tmpl_name = template.name.replace(u'Réponse', 'Message')
        elif claim.first_email is False:
            tmpl_name = template.name.replace(u'Réponse', 'New')
            obj.write(cr,uid,msg.res_id,{'first_email':True})
        else:
            tmpl_name = template.name.replace(u'Réponse', 'Followup')

        tmpl_ids=tmpl_obj.search(cr,uid,[('name','=',tmpl_name)])
        tmpl_obj.send_mail(cr, uid, tmpl_ids[0], msg_id, force_send=True, context=context)

As this function works with mail.message (msg_id parameter) I'm manipulating mail.message objects, and so email_template creates messages with model = "mail.message" instead of eg "crm.claim" thus the reply is made to a message, and not a document.