Allow to extend PatternMatcherFilters via method call

Instead of requiring plugins to overwrite the .matchers method,
they can now call .append_matcher with their custom matcher.

config/initializers/text_formatting.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+#-- 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.
+#++
+
+Rails.application.configure do |application|
+  application.config.to_prepare do
+    namespace = OpenProject::TextFormatting
+
+    namespace::Filters::PatternMatcherFilter.append_matcher namespace::Matchers::ResourceLinksMatcher
+    namespace::Filters::PatternMatcherFilter.append_matcher namespace::Matchers::WikiLinksMatcher
+    namespace::Filters::PatternMatcherFilter.append_matcher namespace::Matchers::AttributeMacros
+  end
+end

lib/open_project/text_formatting/filters/pattern_matcher_filter.rb

@@ -34,12 +34,14 @@ module OpenProject::TextFormatting
       # Skip text nodes that are within preformatted blocks
       PREFORMATTED_BLOCKS = %w(pre code).to_set
 
-      def self.matchers
-        [
-          OpenProject::TextFormatting::Matchers::ResourceLinksMatcher,
-          OpenProject::TextFormatting::Matchers::WikiLinksMatcher,
-          OpenProject::TextFormatting::Matchers::AttributeMacros
-        ]
+      class << self
+        def append_matcher(matcher)
+          matchers << matcher
+        end
+
+        def matchers
+          @matchers ||= []
+        end
       end
 
       def call