Add OpenProject Gitea integration plugin

Implements a Gitea integration for OpenProject following the same
patterns as the bundled GitHub and GitLab integrations.

- Webhook endpoint at /webhooks/gitea with HMAC-SHA256 verification
- Handles pull_request and issue_comment events
- Links Gitea PRs to work packages via OP# references or URLs
- Posts journal comments on WPs for PR lifecycle events
- Gitea tab on the work package split view
- V3 API endpoint: GET /api/v3/work_packages/:id/gitea_pull_requests
- Admin settings UI for bot user and webhook secret
- Nightly cron job to clean up unlinked PR records

lib/open_project/gitea_integration/patches/api/work_package_representer.rb

@@ -0,0 +1,60 @@
+#-- copyright
+# OpenProject is an open source project management software.
+# Copyright (C) the OpenProject GmbH
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+# Copyright (C) 2006-2013 Jean-Philippe Lang
+# Copyright (C) 2010-2013 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+# See COPYRIGHT and LICENSE files for more details.
+#++
+
+module OpenProject::GiteaIntegration
+  module Patches
+    module API
+      module WorkPackageRepresenter
+        module_function
+
+        def extension
+          ->(*) do
+            link :gitea,
+                 cache_if: -> { current_user.allowed_in_work_package?(:show_gitea_content, represented) } do
+              next if represented.new_record?
+
+              {
+                href: "#{work_package_path(id: represented.id)}/tabs/gitea",
+                title: "gitea"
+              }
+            end
+
+            link :gitea_pull_requests do
+              next if represented.new_record?
+
+              {
+                href: api_v3_paths.gitea_pull_requests_by_work_package(represented.id),
+                title: "Gitea pull requests"
+              }
+            end
+          end
+        end
+      end
+    end
+  end
+end