[Fix] UI bugs, Registrations Mail, BTRules Popup, Legacy API fixes (#309)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#309

epdb/tasks.py

@@ -7,6 +7,7 @@ from uuid import uuid4
 from celery import shared_task
 from celery.utils.functional import LRUCache
 from django.conf import settings as s
+from django.core.mail import EmailMultiAlternatives
 from django.utils import timezone
 
 from epdb.logic import SPathway
@@ -73,7 +74,31 @@ def predict_simple(model_pk: int, smiles: str):
 
 @shared_task(queue="background")
 def send_registration_mail(user_pk: int):
-    pass
+    u = User.objects.get(id=user_pk)
+
+    tpl = """Welcome {username}!,
+
+Thank you for your interest in enviPath.
+
+The public system is intended for non-commercial use only.
+We will review your account details and usually activate your account within 24 hours.
+Once activated, you will be notified by email.
+
+If we have any questions, we will contact you at this email address.
+
+Best regards,
+
+enviPath team"""
+
+    msg = EmailMultiAlternatives(
+        "Your enviPath account",
+        tpl.format(username=u.username),
+        "admin@envipath.org",
+        [u.email],
+        bcc=["admin@envipath.org"],
+    )
+
+    msg.send(fail_silently=False)
 
 
 @shared_task(bind=True, queue="model")