title: Topic name case sensitivity and `condition` || not working
body: <p>I have built spring java service using API logic in firebase cloud messaging. </p>
  
  <p>Here is the URL for sample spring service <a href="https://github.com/petq01/firebase-spring-service" rel="nofollow noreferrer">https://github.com/petya0111/firebase-spring-service</a></p>
  
  <p>Reproduce: set the request</p>
  
  <p>Run project</p>
  
  <pre><code>POST http://localhost:8080/notification/messages
  
  Headers: 
  firebase-server-key : [your generated server key]
  Body:
  
  {
      "condition": " 'topic' in topics",
      "title": "Hello,Via Multiple Topics",
      "body": "Hello,Via Multiple Topics"
  }
  </code></pre>
  
  <p>To send messages to condition you must first create topic </p>
  
  <p>Reproduce: create topic</p>
  
  <pre><code>POST https://iid.googleapis.com/iid/v1/{token}/rel/topics/{topic}
  
  headers 
  Authorization  : key=[firebase-server-key]
  
  200 OK 
  </code></pre>
  
  <p>According to the API's documentation, condition field is defined as case-insensitive.
  But in practice, it is actually case sensitive.</p>
  
  <p>I am doing two tests with the same topic name (using upper and lower case chars). The original name of the topic I'm trying to send a message is defined as "Topic". Since the field must be case-insensitive, I am trying to use "topiC" and it should still send the message. Unfortunately, it doesn't. The field is actually case-sensitive and this is a huge problem from my perspective. </p>
  
  <p>My second question:</p>
  
  <p>When a non-existent topic is presented. Exchange with URL <a href="https://fcm.googleapis.com/fcm/send" rel="nofollow noreferrer">https://fcm.googleapis.com/fcm/send</a> doesn't return an error.</p>
  
  <p>My third question on this topic is:
  Condition OR '||'</p>
  
  <pre><code> "condition": "  'topicChrome' in topics || 'topicFirefox' in topics "
  </code></pre>
  
  <p>is not working, I have subscribed one token on topic 'topicChrome' and another token on topic 'topicFirefox'.</p>