title: HashiCorp Vault project - write additional key/value pair without overwritting existing ones
body: <p>When I put the first key/value pair to Vault:</p>
  
  <pre><code>vault write secret/item/33 item_name='item_name' 
  </code></pre>
  
  <p>It works well and I get:</p>
  
  <pre><code>vault read secret/item/33
  
  Key                     Value
  ---                     -----
  refresh_interval        768h0m0s
  item_name               item_name
  </code></pre>
  
  <p>But if I want put additional field <code>item_type</code>:</p>
  
  <pre><code>vault write secret/item/33 item_type='item_type' 
  </code></pre>
  
  <p>It overwrites existing one:</p>
  
  <pre><code>vault read secret/item/33
  
  Key                     Value
  ---                     -----
  refresh_interval        768h0m0s
  item_type               item_type
  </code></pre>
  
  <p>How to write additional field - key/value pair to Vault without replacing existing ones?</p>