Add email body_html template (django-otp#112)

- Add the requested tests for the linked pull request

docs/source/overview.rst

@@ -433,6 +433,21 @@ 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.
 
 
+.. setting:: OTP_EMAIL_BODY_HTML_TEMPLATE
+
+**OTP_EMAIL_BODY_HTML_TEMPLATE**
+
+Default: ``None``
+
+A raw template string to use for the email html alternative body. The render context will
+include the generated token in the ``token`` key. Additional template context
+may be passed to
+:meth:`~django_otp.plugins.otp_email.models.EmailDevice.generate_challenge`.
+
+If this and :setting:`OTP_EMAIL_BODY_HTML_TEMPLATE_PATH` are not set, we won't attach any
+html alternative to the email.
+
+
 .. setting:: OTP_EMAIL_BODY_TEMPLATE_PATH
 
 **OTP_EMAIL_BODY_TEMPLATE_PATH**
@@ -448,6 +463,21 @@ 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.
 
 
+.. setting:: OTP_EMAIL_BODY_HTML_TEMPLATE_PATH
+
+**OTP_EMAIL_BODY_HTML_TEMPLATE_PATH**
+
+Default: ``None``
+
+A path string to a template file to use for the email html alternative body. The render context
+will include the generated token in the ``token`` key. Additional template
+context may be passed to
+:meth:`~django_otp.plugins.otp_email.models.EmailDevice.generate_challenge`.
+
+If this and :setting:`OTP_EMAIL_BODY_HTML_TEMPLATE` are not set, we won't attach any html
+alternative to the email.
+
+
 .. setting:: OTP_EMAIL_TOKEN_VALIDITY
 
 **OTP_EMAIL_TOKEN_VALIDITY**

src/django_otp/plugins/otp_email/conf.py

@@ -15,6 +15,8 @@ class OTPEmailSettings:
         'OTP_EMAIL_SUBJECT': 'OTP token',
         'OTP_EMAIL_BODY_TEMPLATE': None,
         'OTP_EMAIL_BODY_TEMPLATE_PATH': 'otp/email/token.txt',
+        'OTP_EMAIL_BODY_HTML_TEMPLATE': None,
+        'OTP_EMAIL_BODY_HTML_TEMPLATE_PATH': None,
         'OTP_EMAIL_TOKEN_VALIDITY': 300,
         'OTP_EMAIL_THROTTLE_FACTOR': 1,
     }

src/django_otp/plugins/otp_email/models.py

@@ -65,12 +65,18 @@ def generate_challenge(self, extra_context=None):
         else:
             body = get_template(settings.OTP_EMAIL_BODY_TEMPLATE_PATH).render(context)
 
-        send_mail(
-            str(settings.OTP_EMAIL_SUBJECT),
-            body,
-            settings.OTP_EMAIL_SENDER,
-            [self.email or self.user.email],
-        )
+        if settings.OTP_EMAIL_BODY_HTML_TEMPLATE:
+            body_html = Template(settings.OTP_EMAIL_BODY_HTML_TEMPLATE).render(Context(context))
+        elif settings.OTP_EMAIL_BODY_HTML_TEMPLATE_PATH:
+            body_html = get_template(settings.OTP_EMAIL_BODY_HTML_TEMPLATE_PATH).render(context)
+        else:
+            body_html = None
+
+        send_mail(settings.OTP_EMAIL_SUBJECT,
+                  body,
+                  settings.OTP_EMAIL_SENDER,
+                  [self.email or self.user.email],
+                  html_message=body_html) 
 
         message = "sent by email"