policies/expression: migrate to raw python instead of jinja2 (#49)

* policies/expression: migrate to raw python instead of jinja2

* lib/expression: create base evaluator, custom subclass for policies

* core: rewrite propertymappings to use python

* providers/saml: update to new PropertyMappings

* sources/ldap: update to new PropertyMappings

* docs: update docs for new propertymappings

* root: remove jinja2

* root: re-add jinja to lock file as its implicitly required

passbook/policies/process.py

@@ -39,6 +39,8 @@ class PolicyProcess(Process):
         super().__init__()
         self.binding = binding
         self.request = request
+        if not isinstance(self.request, PolicyRequest):
+            raise ValueError(f"{self.request} is not a Policy Request.")
         if connection:
             self.connection = connection