Flow exporting/importing (#187)

* stages/*: Add SerializerModel as base model, implement serializer property

* flows: add initial flow exporter and importer

* policies/*: implement .serializer for all policies

* root: fix missing dacite requirement

passbook/policies/password/models.py

@@ -5,6 +5,7 @@ from typing import Type
 from django.db import models
 from django.forms import ModelForm
 from django.utils.translation import gettext as _
+from rest_framework.serializers import BaseSerializer
 from structlog import get_logger
 
 from passbook.policies.models import Policy
@@ -30,6 +31,12 @@ class PasswordPolicy(Policy):
     symbol_charset = models.TextField(default=r"!\"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ ")
     error_message = models.TextField()
 
+    @property
+    def serializer(self) -> BaseSerializer:
+        from passbook.policies.password.api import PasswordPolicySerializer
+
+        return PasswordPolicySerializer
+
     def form(self) -> Type[ModelForm]:
         from passbook.policies.password.forms import PasswordPolicyForm