WIP Use Flows for Sources and Providers (#32)

* core: start migrating to flows for authorisation

* sources/oauth: start type-hinting

* core: create default user

* core: only show user delete button if an unenrollment flow exists

* flows: Correctly check initial policies on flow with context

* policies: add more verbosity to engine

* sources/oauth: migrate to flows

* sources/oauth: fix typing errors

* flows: add more tests

* sources/oauth: start implementing unittests

* sources/ldap: add option to disable user sync, move connection init to model

* sources/ldap: re-add default PropertyMappings

* providers/saml: re-add default PropertyMappings

* admin: fix missing stage count

* stages/identification: fix sources not being shown

* crypto: fix being unable to save with private key

* crypto: re-add default self-signed keypair

* policies: rewrite cache_key to prevent wrong cache

* sources/saml: migrate to flows for auth and enrollment

* stages/consent: add new stage

* admin: fix PropertyMapping widget not rendering properly

* core: provider.authorization_flow is mandatory

* flows: add support for "autosubmit" attribute on form

* flows: add InMemoryStage for dynamic stages

* flows: optionally allow empty flows from FlowPlanner

* providers/saml: update to authorization_flow

* sources/*: fix flow executor URL

* flows: fix pylint error

* flows: wrap responses in JSON object to easily handle redirects

* flow: dont cache plan's context

* providers/oauth: rewrite OAuth2 Provider to use flows

* providers/*: update docstrings of models

* core: fix forms not passing help_text through safe

* flows: fix HttpResponses not being converted to JSON

* providers/oidc: rewrite to use flows

* flows: fix linting

passbook/providers/saml/models.py

@@ -17,6 +17,13 @@ from passbook.providers.saml.utils.time import timedelta_string_validator
 LOGGER = get_logger()
 
 
+class SAMLBindings(models.TextChoices):
+    """SAML Bindings supported by passbook"""
+
+    REDIRECT = "redirect"
+    POST = "post"
+
+
 class SAMLProvider(Provider):
     """Model to save information about a Remote SAML Endpoint"""
 
@@ -26,6 +33,9 @@ class SAMLProvider(Provider):
     acs_url = models.URLField(verbose_name=_("ACS URL"))
     audience = models.TextField(default="")
     issuer = models.TextField(help_text=_("Also known as EntityID"))
+    sp_binding = models.TextField(
+        choices=SAMLBindings.choices, default=SAMLBindings.REDIRECT
+    )
 
     assertion_valid_not_before = models.TextField(
         default="minutes=-5",
@@ -118,8 +128,8 @@ class SAMLProvider(Provider):
         try:
             # pylint: disable=no-member
             return reverse(
-                "passbook_providers_saml:saml-metadata",
-                kwargs={"application": self.application.slug},
+                "passbook_providers_saml:metadata",
+                kwargs={"application_slug": self.application.slug},
             )
         except Provider.application.RelatedObjectDoesNotExist:
             return None