👔(backend) add Organization model

We introduce the Organization model has a "hat" for all
users and team.

Each User must have a "default" organization.
Each Team must have an organization.

When a User creates a new Team, the team is linked to their
default Organization.

For now the Organization should not be visible to end users
this is a purely technical aspect as it.

The models are also adding a permission to allow User to edit
an Organization, but for now there are no endpoints for that.

Next steps:
- Add an Organization to each User and Team on all environments
  to mark Organization as mandatory in database.
- Add scope to Organization to list the Service Provider list
  allowed for a User in an Organization.
- Add endpoints + frontend to manage Organization's scopes

src/backend/core/admin.py

@@ -18,6 +18,15 @@ class TeamAccessInline(admin.TabularInline):
     readonly_fields = ("created_at", "updated_at")
 
 
+class OrganizationAccessInline(admin.TabularInline):
+    """Inline admin class for organization accesses."""
+
+    autocomplete_fields = ["user", "organization"]
+    extra = 0
+    model = models.OrganizationAccess
+    readonly_fields = ("created_at", "updated_at")
+
+
 class TeamWebhookInline(admin.TabularInline):
     """Inline admin class for team webhooks."""
 
@@ -31,6 +40,7 @@ class TeamWebhookInline(admin.TabularInline):
 class UserAdmin(auth_admin.UserAdmin):
     """Admin class for the User model"""
 
+    autocomplete_fields = ["organization"]
     fieldsets = (
         (
             None,
@@ -67,9 +77,10 @@ class UserAdmin(auth_admin.UserAdmin):
             },
         ),
     )
-    inlines = (TeamAccessInline, MailDomainAccessInline)
+    inlines = (TeamAccessInline, MailDomainAccessInline, OrganizationAccessInline)
     list_display = (
         "get_user",
+        "organization",
         "created_at",
         "updated_at",
         "is_active",
@@ -176,3 +187,30 @@ class ContactAdmin(admin.ModelAdmin):
         "owner",
         "base",
     )
+
+
+@admin.register(models.Organization)
+class OrganizationAdmin(admin.ModelAdmin):
+    """Admin interface for organizations."""
+
+    list_display = (
+        "name",
+        "created_at",
+        "updated_at",
+    )
+    search_fields = ("name",)
+    inlines = (OrganizationAccessInline,)
+
+
+@admin.register(models.OrganizationAccess)
+class OrganizationAccessAdmin(admin.ModelAdmin):
+    """Organization access admin interface declaration."""
+
+    autocomplete_fields = ("user", "organization")
+    list_display = (
+        "user",
+        "organization",
+        "role",
+        "created_at",
+        "updated_at",
+    )