providers/saml: big cleanup, simplify base processor

add New fields for
 - assertion_valid_not_before
 - assertion_valid_not_on_or_after
 - session_valid_not_on_or_after
allow flexible time durations for these fields
fall back to Provider's ACS if none is specified in AuthNRequest

passbook/providers/saml/tests/test_utils_time.py

@@ -0,0 +1,30 @@
+"""Test time utils"""
+from datetime import timedelta
+
+from django.core.exceptions import ValidationError
+from django.test import TestCase
+
+from passbook.providers.saml.utils.time import (
+    timedelta_from_string,
+    timedelta_string_validator,
+)
+
+
+class TestTimeUtils(TestCase):
+    """Test time-utils"""
+
+    def test_valid(self):
+        """Test valid expression"""
+        expr = "hours=3;minutes=1"
+        expected = timedelta(hours=3, minutes=1)
+        self.assertEqual(timedelta_from_string(expr), expected)
+
+    def test_invalid(self):
+        """Test invalid expression"""
+        with self.assertRaises(ValueError):
+            timedelta_from_string("foo")
+
+    def test_validation(self):
+        """Test Django model field validator"""
+        with self.assertRaises(ValidationError):
+            timedelta_string_validator("foo")