fix(backend): validate length of instance actor details and set description column to text

Closes #1393

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20240104103036_change_actor_instance_description_type_to_text.exs

@@ -0,0 +1,15 @@
+defmodule Mobilizon.Storage.Repo.Migrations.ChangeActorInstanceDescriptionTypeToText do
+  use Ecto.Migration
+
+  def up do
+    alter table(:instance_actors) do
+      modify(:instance_description, :text)
+    end
+  end
+
+  def down do
+    alter table(:instance_actors) do
+      modify(:instance_description, :string)
+    end
+  end
+end