Fix the admin new/edit views for projects after changing the form

The budget was not passed as a context variable to the form
objects in the new/edit views.

app/controllers/concerns/decidim/budgeting_pipeline/admin/projects_controller_extensions.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Decidim
+  module BudgetingPipeline
+    module Admin
+      # Customizes the admin projects controller to fix a bug on passing the
+      # budget through the form context.
+      module ProjectsControllerExtensions
+        extend ActiveSupport::Concern
+
+        included do
+          def new
+            enforce_permission_to :create, :project
+            @form = form(Decidim::Budgets::Admin::ProjectForm).from_params(
+              { attachment: form(AttachmentForm).instance },
+              budget: budget
+            )
+          end
+
+          def edit
+            enforce_permission_to :update, :project, project: project
+            @form = form(Decidim::Budgets::Admin::ProjectForm).from_model(project, budget: budget)
+            @form.attachment = form(AttachmentForm).instance
+          end
+        end
+      end
+    end
+  end
+end

lib/decidim/budgeting_pipeline/engine.rb

@@ -146,6 +146,9 @@ class Engine < ::Rails::Engine
           Decidim::Budgets::Admin::BudgetsController.include(
             Decidim::BudgetingPipeline::Admin::BudgetsControllerExtensions
           )
+          Decidim::Budgets::Admin::ProjectsController.include(
+            Decidim::BudgetingPipeline::Admin::ProjectsControllerExtensions
+          )
 
           # Cell extensions
           Decidim::Budgets::ProjectMCell.include(