DEV: move sidebar community section to database (#21166)

* DEV: move sidebar community section to database

Before, community section was hard-coded. In the future, we are planning to allow admins to edit it. Therefore, it has to be moved to database to `custom_sections` table.

Few steps and simplifications has to be made:
- custom section was hidden behind `enable_custom_sidebar_sections` feature flag. It has to be deleted so all forums, see community section;
- migration to add `section_type` column to sidebar section to show it is a special type;
- migration to add `segment` column to sidebar links to determine if link should be displayed in primary section or in more section;
- simplify more section to have one level only (secondary section links are merged);
- ensure that links like `everything` are correctly tracking state;
- make user an anonymous links position consistence. For example, from now on `faq` link for user and anonymous is visible in more tab;
- delete old community-section template.

app/controllers/sidebar_sections_controller.rb

@@ -2,7 +2,6 @@
 
 class SidebarSectionsController < ApplicationController
   requires_login
-  before_action :check_if_member_of_group
   before_action :check_access_if_public
 
   def index
@@ -20,11 +19,7 @@ class SidebarSectionsController < ApplicationController
 
     if sidebar_section.public?
       StaffActionLogger.new(current_user).log_create_public_sidebar_section(sidebar_section)
-      MessageBus.publish(
-        "/refresh-sidebar-sections",
-        nil,
-        group_ids: SiteSetting.enable_custom_sidebar_sections_map,
-      )
+      MessageBus.publish("/refresh-sidebar-sections", nil)
       Site.clear_anon_cache!
     end
 
@@ -44,11 +39,7 @@ class SidebarSectionsController < ApplicationController
 
     if sidebar_section.public?
       StaffActionLogger.new(current_user).log_update_public_sidebar_section(sidebar_section)
-      MessageBus.publish(
-        "/refresh-sidebar-sections",
-        nil,
-        group_ids: SiteSetting.enable_custom_sidebar_sections_map,
-      )
+      MessageBus.publish("/refresh-sidebar-sections", nil)
       Site.clear_anon_cache!
     end
 
@@ -86,11 +77,7 @@ class SidebarSectionsController < ApplicationController
 
     if sidebar_section.public?
       StaffActionLogger.new(current_user).log_destroy_public_sidebar_section(sidebar_section)
-      MessageBus.publish(
-        "/refresh-sidebar-sections",
-        nil,
-        group_ids: SiteSetting.enable_custom_sidebar_sections_map,
-      )
+      MessageBus.publish("/refresh-sidebar-sections", nil)
     end
     render json: SidebarSectionSerializer.new(sidebar_section)
   rescue Discourse::InvalidAccess
@@ -111,14 +98,6 @@ class SidebarSectionsController < ApplicationController
     params.permit(:sidebar_section_id, links_order: [])
   end
 
-  def check_if_member_of_group
-    ### TODO remove when enable_custom_sidebar_sections SiteSetting is removed
-    if !SiteSetting.enable_custom_sidebar_sections.present? ||
-         !current_user.in_any_groups?(SiteSetting.enable_custom_sidebar_sections_map)
-      raise Discourse::InvalidAccess
-    end
-  end
-
   private
 
   def check_access_if_public