title: How to execute raw mongo queries in Loopback 4
body: <p>I'm evaluating the adoption of Loopback4 for a new project. I studied the tutorial and the documentation and I've to make some test. One of those is related to the capabilities of executing native mongodb queries. </p>
  
  <p>I found a lot of examples related to Loopback v3 but since the structure is quite different (compared to Lb4), they are not reliable. Of course,  I'd like to keep the separation among  model/repository/datasource as designed by Lb4 and I'd like to mantain the typization.
  Does anyone as tryed to do the same thing?
  Every help will be apreciated
  Thanks a lot</p>