✨(backend) add django-treebeard to allow tree structure on documents

We choose to use Django-treebeard for its quality, performance and
stability. Adding tree structure to documents is as simple as
inheriting from the MP_Node class.

src/backend/core/admin.py

@@ -4,12 +4,16 @@ from django.contrib import admin
 from django.contrib.auth import admin as auth_admin
 from django.utils.translation import gettext_lazy as _
 
+from treebeard.admin import TreeAdmin
+from treebeard.forms import movenodeform_factory
+
 from . import models
 
 
 class TemplateAccessInline(admin.TabularInline):
     """Inline admin class for template accesses."""
 
+    autocomplete_fields = ["user"]
     model = models.TemplateAccess
     extra = 0
 
@@ -111,14 +115,47 @@ class TemplateAdmin(admin.ModelAdmin):
 class DocumentAccessInline(admin.TabularInline):
     """Inline admin class for template accesses."""
 
+    autocomplete_fields = ["user"]
     model = models.DocumentAccess
     extra = 0
 
 
 @admin.register(models.Document)
-class DocumentAdmin(admin.ModelAdmin):
+class DocumentAdmin(TreeAdmin):
     """Document admin interface declaration."""
 
+    fieldsets = (
+        (
+            None,
+            {
+                "fields": (
+                    "id",
+                    "title",
+                )
+            },
+        ),
+        (
+            _("Permissions"),
+            {
+                "fields": (
+                    "creator",
+                    "link_reach",
+                    "link_role",
+                )
+            },
+        ),
+        (
+            _("Tree structure"),
+            {
+                "fields": (
+                    "path",
+                    "depth",
+                    "numchild",
+                )
+            },
+        ),
+    )
+    form = movenodeform_factory(models.Document)
     inlines = (DocumentAccessInline,)
     list_display = (
         "id",
@@ -128,6 +165,14 @@ class DocumentAdmin(admin.ModelAdmin):
         "created_at",
         "updated_at",
     )
+    readonly_fields = (
+        "creator",
+        "depth",
+        "id",
+        "numchild",
+        "path",
+    )
+    search_fields = ("id", "title")
 
 
 @admin.register(models.Invitation)