Add system checks to dashboard in admin UI (#15989)

app/lib/admin/system_check/message.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class Admin::SystemCheck::Message
+  attr_reader :key, :value, :action
+
+  def initialize(key, value = nil, action = nil)
+    @key    = key
+    @value  = value
+    @action = action
+  end
+end