Add ability to filter individual posts (#18945)

* Add database table for status-specific filters

* Add REST endpoints, entities and attributes

* Show status filters in /filters interface

* Perform server-side filtering for individual posts filters

* Fix filtering on context mismatch

* Refactor `toServerSideType` by moving it to its own module

* Move loupe and delete icons to their own module

* Add ability to filter individual posts from WebUI

* Replace keyword list by warnings (expired, context mismatch)

* Refactor server-side filtering code

* Add tests

db/migrate/20220808101323_create_custom_filter_statuses.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class CreateCustomFilterStatuses < ActiveRecord::Migration[6.1]
+  def change
+    create_table :custom_filter_statuses do |t|
+      t.belongs_to :custom_filter, foreign_key: { on_delete: :cascade }, null: false
+      t.belongs_to :status, foreign_key: { on_delete: :cascade }, null: false
+
+      t.timestamps
+    end
+  end
+end