Fix user admin object creation and deletion; DMOJ/online-judge#931, D…

…MOJ/online-judge#2288

- Automatically create profile when adding a user through admin
- Disallow adding profiles through admin
- (Soft) disallow deleting profiles through admin

judge/admin/__init__.py

@@ -1,13 +1,14 @@
 from django.contrib import admin
 from django.contrib.admin.models import LogEntry
+from django.contrib.auth.models import User
 from django.contrib.flatpages.models import FlatPage
 
 from judge.admin.comments import CommentAdmin
 from judge.admin.contest import ContestAdmin, ContestParticipationAdmin, ContestTagAdmin
 from judge.admin.interface import BlogPostAdmin, FlatPageAdmin, LicenseAdmin, LogEntryAdmin, NavigationBarAdmin
 from judge.admin.organization import OrganizationAdmin, OrganizationRequestAdmin
 from judge.admin.problem import ProblemAdmin
-from judge.admin.profile import ProfileAdmin
+from judge.admin.profile import ProfileAdmin, UserAdmin
 from judge.admin.runtime import JudgeAdmin, LanguageAdmin
 from judge.admin.submission import SubmissionAdmin
 from judge.admin.tag import TagAdmin, TagGroupAdmin, TagProblemAdmin
@@ -44,3 +45,5 @@
 admin.site.register(Tag, TagAdmin)
 admin.site.register(TagGroup, TagGroupAdmin)
 admin.site.register(TagProblem, TagProblemAdmin)
+admin.site.unregister(User)
+admin.site.register(User, UserAdmin)

judge/admin/profile.py

@@ -1,4 +1,5 @@
 from django.contrib import admin
+from django.contrib.auth.admin import UserAdmin as OldUserAdmin
 from django.forms import ModelForm
 from django.urls import reverse_lazy
 from django.utils.html import format_html
@@ -73,6 +74,17 @@ class ProfileAdmin(NoBatchDeleteMixin, VersionAdmin):
     form = ProfileForm
     inlines = [WebAuthnInline]
 
+    def has_add_permission(self, request, obj=None):
+        return False
+
+    # We can't use has_delete_permission here because we still want user profiles to be
+    # deleteable through related objects (i.e. User). Thus, we simply hide the delete button.
+    # If an admin wants to go directly to the delete endpoint to delete a profile, more
+    # power to them.
+    def render_change_form(self, request, context, **kwargs):
+        context['show_delete'] = False
+        return super().render_change_form(request, context, **kwargs)
+
     def get_queryset(self, request):
         return super(ProfileAdmin, self).get_queryset(request).select_related('user')
 
@@ -140,3 +152,10 @@ def get_form(self, request, obj=None, **kwargs):
                 mode='javascript', theme=request.profile.resolved_ace_theme,
             )
         return form
+
+
+class UserAdmin(OldUserAdmin):
+    def save_model(self, request, obj, form, change):
+        super().save_model(request, obj, form, change)
+        if not change:
+            Profile.objects.create(user=obj)