Add ability to pass extra context when rendering email templates (#82)

Add ability to pass extra context when rendering email templates.

docs/source/overview.rst

@@ -415,6 +415,9 @@ Default: ``None``
 A raw template string to use for the email body. The render context will
 include the generated token in the ``token`` key.
 
+Dictionary sent to :meth:`~django_otp.plugins.otp_email.models.EmailDevice.generate_challenge`
+under ``extra_context`` will be also used as context for building the email.
+
 If this and :setting:`OTP_EMAIL_BODY_TEMPLATE_PATH` are not set, we'll render
 the template 'otp/email/token.txt', which you'll most likely want to override.
 
@@ -428,6 +431,9 @@ Default: ``otp/email/token.txt``
 A path string to a template file to use for the email body. The render context
 will include the generated token in the ``token`` key.
 
+Dictionary sent to :meth:`~django_otp.plugins.otp_email.models.EmailDevice.generate_challenge`
+under ``extra_context`` will be also used as context for building the email.
+
 If this and :setting:`OTP_EMAIL_BODY_TEMPLATE` are not set, we'll render the
 template 'otp/email/token.txt', which you'll most likely want to override.
 

src/django_otp/plugins/otp_email/models.py

@@ -47,13 +47,17 @@ class EmailDevice(ThrottlingMixin, SideChannelDevice):
     def get_throttle_factor(self):
         return settings.OTP_EMAIL_THROTTLE_FACTOR
 
-    def generate_challenge(self):
+    def generate_challenge(self, extra_context=None):
         """
         Generates a random token and emails it to the user.
+
+        :param extra_context: If provided, the dictionary will be used as context,
+            along with the token, for generating the email. Default is ``None``.
+        :type extra_context: dict
         """
         self.generate_token(valid_secs=settings.OTP_EMAIL_TOKEN_VALIDITY)
 
-        context = {'token': self.token}
+        context = {'token': self.token, **(extra_context or {})}
         if settings.OTP_EMAIL_BODY_TEMPLATE:
             body = Template(settings.OTP_EMAIL_BODY_TEMPLATE).render(Context(context))
         else:

src/django_otp/plugins/otp_email/tests.py

@@ -132,6 +132,29 @@ def test_settings_template_path(self):
         with self.subTest(field='body'):
             self.assertEqual(msg.body, "Test template 3: {}\n".format(self.device.token))
 
+    @override_settings(
+        OTP_EMAIL_SENDER="webmaster@example.com",
+        OTP_EMAIL_SUBJECT="Test subject",
+        OTP_EMAIL_BODY_TEMPLATE="Test template 4: {{token}} {{foo}} {{bar}}",
+    )
+    def test_settings_extra_template_options(self):
+        extra_context = {"foo": "extra 1", "bar": "extra 2"}
+        self.device.generate_challenge(extra_context)
+
+        self.assertEqual(len(mail.outbox), 1)
+
+        msg = mail.outbox[0]
+
+        with self.subTest(field='from_email'):
+            self.assertEqual(msg.from_email, "webmaster@example.com")
+        with self.subTest(field='subject'):
+            self.assertEqual(msg.subject, "Test subject")
+        with self.subTest(field='body'):
+            self.assertEqual(
+                msg.body,
+                "Test template 4: {} {} {}".format(self.device.token, extra_context["foo"], extra_context["bar"])
+            )
+
     def test_alternative_email(self):
         self.device.email = 'alice2@example.com'
         self.device.save()