fix: send reset emails

At the moment, the email is stored in the `username` field.

Django form-handling looks for the default email
field [0] to find the user email.

If it doesnet find anything, it fails silently
(to avoid leaking information about the users
present in the system, which is a good thing)

The fix was to change the field used to check for the email.

[0] eea4f92f9a/django/contrib/auth/forms.py (L326-L337)

la_chariotte/accounts/models.py

@@ -3,6 +3,8 @@ from django.db import models
 
 
 class CustomUser(AbstractUser):
+    EMAIL_FIELD = "username"
+
     username = models.EmailField(
         "Email",
         unique=True,