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/engine.rb

@@ -0,0 +1,123 @@
+#-- 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.
+#++
+
+require "open_project/plugins"
+
+require_relative "patches/api/work_package_representer"
+require_relative "notification_handlers"
+require_relative "hook_handler"
+require_relative "services"
+
+module OpenProject::GiteaIntegration
+  class Engine < ::Rails::Engine
+    engine_name :openproject_gitea_integration
+
+    include OpenProject::Plugins::ActsAsOpEngine
+
+    def self.settings
+      {
+        default: {
+          "gitea_user_id" => nil,
+          "webhook_secret" => nil
+        }
+      }
+    end
+
+    register "openproject-gitea_integration",
+             author_url: "https://www.openproject.org",
+             bundled: false,
+             settings: do
+      ::Redmine::MenuManager.map(:admin_menu) do |menu|
+        menu.push :admin_gitea_integration,
+                  { controller: "/gitea_integration/admin/settings", action: "show" },
+                  parent: :admin_integrations,
+                  if: ->(_) { User.current.admin? },
+                  caption: "Gitea",
+                  icon: :"op-logo-gitea"
+      end
+
+      project_module(:gitea, dependencies: :work_package_tracking) do
+        permission(:show_gitea_content,
+                   {},
+                   permissible_on: %i[work_package project])
+      end
+
+      menu :work_package_split_view,
+           :gitea,
+           { tab: :gitea },
+           if: ->(project) {
+             User.current.allowed_in_project?(:show_gitea_content, project)
+           },
+           skip_permissions_check: true,
+           badge: ->(work_package:, **) {
+             work_package.gitea_pull_requests.count
+           },
+           before: :watchers,
+           caption: :project_module_gitea
+    end
+
+    patches %w[WorkPackage]
+
+    initializer "gitea.register_hook" do
+      ::OpenProject::Webhooks.register_hook "gitea" do |hook, environment, params, user|
+        HookHandler.new.process(hook, environment, params, user)
+      end
+    end
+
+    initializer "gitea.subscribe_to_notifications" do
+      ::OpenProject::Notifications.subscribe("gitea.pull_request",
+                                             &NotificationHandlers.method(:pull_request))
+      ::OpenProject::Notifications.subscribe("gitea.issue_comment",
+                                             &NotificationHandlers.method(:issue_comment))
+    end
+
+    extend_api_response(:v3, :work_packages, :work_package,
+                        &::OpenProject::GiteaIntegration::Patches::API::WorkPackageRepresenter.extension)
+
+    add_api_path :gitea_pull_requests_by_work_package do |id|
+      "#{work_package(id)}/gitea_pull_requests"
+    end
+
+    add_api_path :gitea_user do |id|
+      "gitea_users/#{id}"
+    end
+
+    add_api_endpoint "API::V3::WorkPackages::WorkPackagesAPI", :id do
+      mount ::API::V3::GiteaPullRequests::GiteaPullRequestsByWorkPackageAPI
+    end
+
+    add_cron_jobs do
+      {
+        "Cron::ClearOldGiteaPullRequestsJob": {
+          cron: "25 1 * * *",
+          class: ::Cron::ClearOldGiteaPullRequestsJob.name
+        }
+      }
+    end
+  end
+end