title: Mongoengine Database cannot change Database
body: <p>At our company we have a standard connection string format to connect to a mongodb database, for example:
  <code>mongodb://&lt;some_user&gt;:&lt;some_password&gt;@&lt;some_host&gt;.mongodb.net/admin&amp;authSource=admin</code></p>
  <p>When i register the connection with mongoengine
  <code>connect(host=&lt;connection_string&gt;, db=&quot;my_db&quot;)</code> the db to be accessed remains <code>admin</code> and <code>my_db</code> is not used. What I need is to override the database given by our standard connection string with the database I actually want to use.
  I tried to use the method <code>switch_db</code> but as the method needs to be using a db-alias of a predefined connection, this is also not possible.</p>
  <p>I know, a solution would be to change the connection-string by chaning the initial database name. But I need a solution to be able to dynamically change database name without changing the uri.</p>
  <p>Any ideas?</p>