title: RSpec: Is there a way to check for a nested hash key at any level?
body: <p>I expect my hash to look like one of these two: </p>
  
  <pre><code>{metadata: {SOME_UNKNOWN_KEY: {transaction_id: 123456}}}
  {metadata: {transaction_id: 123456}}
  </code></pre>
  
  <p>If I'm looking for the key <code>:transaction_id</code>, I understand that I can use <code>hash_including</code> to expect a nested key that should be in a particular place, but I'd like to be able to do something like this to cover both options: </p>
  
  <pre><code>expect(something).
    to receive(some_method).
    with(hash_including(metadata: hash_including_anywhere(:transaction_id)))
  </code></pre>
  
  <p>Is this possible?</p>