new_contents: 
  
  class Router(object):
      """
      A router to control all database operations between the 2 apps
      """
      def db_for_read(self, model, **hints):
          if model._meta.app_label == 'eve':
              return 'eve'
          if model._meta.app_label == 'presta':
              return 'presta'
          return None
  
      def db_for_write(self, model, **hints):
          if model._meta.app_label == 'eve':
              return 'eve'
          if model._meta.app_label == 'presta':
              return 'presta'
          return None
  
      def allow_relation(self, obj1, obj2, **hints):
          if obj1._meta.app_label == 'eve' or \
             obj2._meta.app_label == 'eve':
             return True
          if obj1._meta.app_label == 'presta' or \
             obj2._meta.app_label == 'presta':
             return True
          return None
  
      def allow_migrate(self, db, app_label, model=None, **hints):
          if app_label == 'eve':
              return db == 'eve'
          if app_label == 'presta':
              return db == 'presta'
          return None
  
subject: add router