'Update workflow type configuration
- update the workflow model (for base (model_id) /relational (field.relation))
- update wkf_transition_id to False if workflow model changes, to force
the user to choose a new one'

@api.onchange('use_relational_model', 'wkf_field_id')
def _onchange_wkf_config(self):

    if ((self.use_relational_model == 'relational') and self.wkf_field_id):
        field = self.wkf_field_id
        self.wkf_model_id = self.env['ir.model'].search([('model', '=', field.relation)])
    else:
        self.wkf_model_id = self.model_id
