✨(admin) configure a minimum admin with users and teams

We added identities and team accesses as inlines.

src/backend/core/admin.py

@@ -0,0 +1,111 @@
+"""Admin classes and registrations for People's core app."""
+from django import forms
+from django.contrib import admin
+from django.contrib.auth import admin as auth_admin
+from django.utils.translation import gettext_lazy as _
+
+from . import models
+
+
+class IdentityFormSet(forms.BaseInlineFormSet):
+    """
+    Make the "is_main" field readonly when it is True so that declaring another identity
+    works in the admin.
+    """
+
+    def add_fields(self, form, index):
+        """Disable the "is_main" field when it is set to True"""
+        super().add_fields(form, index)
+        is_main_value = form.instance.is_main if form.instance else False
+        form.fields["is_main"].disabled = is_main_value
+
+
+class IdentityInline(admin.TabularInline):
+    """Inline admin class for user identities."""
+
+    fields = (
+        "sub",
+        "email",
+        "is_main",
+        "created_at",
+        "updated_at",
+    )
+    formset = IdentityFormSet
+    model = models.Identity
+    extra = 0
+    readonly_fields = ("email", "created_at", "sub", "updated_at")
+
+    def has_add_permission(self, request, obj):
+        """
+        Identities are automatically created on successful OIDC logins.
+        Disable creating identities via the admin.
+        """
+        return False
+
+
+class TeamAccessInline(admin.TabularInline):
+    """Inline admin class for team accesses."""
+
+    extra = 0
+    autocomplete_fields = ["user", "team"]
+    model = models.TeamAccess
+    readonly_fields = ("created_at", "updated_at")
+
+
+@admin.register(models.User)
+class UserAdmin(auth_admin.UserAdmin):
+    """Admin class for the User model"""
+
+    fieldsets = (
+        (
+            None,
+            {
+                "fields": (
+                    "id",
+                    "password",
+                )
+            },
+        ),
+        (_("Personal info"), {"fields": ("email", "language", "timezone")}),
+        (
+            _("Permissions"),
+            {
+                "fields": (
+                    "is_active",
+                    "is_device",
+                    "is_staff",
+                    "is_superuser",
+                    "groups",
+                    "user_permissions",
+                ),
+            },
+        ),
+        (_("Important dates"), {"fields": ("created_at", "updated_at")}),
+    )
+    inlines = (IdentityInline, TeamAccessInline)
+    list_display = (
+        "email",
+        "created_at",
+        "updated_at",
+        "is_active",
+        "is_device",
+        "is_staff",
+        "is_superuser",
+    )
+    list_filter = ("is_staff", "is_superuser", "is_device", "is_active")
+    ordering = ("is_active", "-is_superuser", "-is_staff", "-is_device", "-updated_at")
+    readonly_fields = ("id", "created_at", "updated_at")
+    search_fields = ("id", "email", "identities__sub", "identities__email")
+
+
+@admin.register(models.Team)
+class TeamAdmin(admin.ModelAdmin):
+    """Team admin interface declaration."""
+
+    inlines = (TeamAccessInline,)
+    list_display = (
+        "name",
+        "created_at",
+        "updated_at",
+    )
+    search_fields = ("name",)