✨(contacts) add notes & force full_name

We make the full name mandatory and add a field to
allow user to store personnal notes on the contact.

This also make the "base" contact not mandatory because
user may want to create new contacts out of the blue.

src/backend/core/models.py

@@ -113,11 +113,11 @@ class Contact(BaseModel):
         null=True,
         blank=True,
     )
-    full_name = models.CharField(_("full name"), max_length=150, null=True, blank=True)
+    full_name = models.CharField(_("full name"), max_length=150)
     short_name = models.CharField(_("short name"), max_length=30, null=True, blank=True)
 
     # avatar =
-    # notes =
+    notes = models.TextField(_("notes"), blank=True, default="")
     data = models.JSONField(
         _("contact information"),
         help_text=_("A JSON object containing the contact information"),
@@ -151,7 +151,7 @@ class Contact(BaseModel):
         ]
 
     def __str__(self):
-        return self.full_name or self.short_name
+        return self.full_name
 
     def clean(self):
         """Validate fields."""