Service Bus can crash if it receives a malformed payload

**Describe the bug**
Currently the service bus will crash if it receives a malformed/non-JSON messages

**Steps to reproduce**

1. Send invalid json to the service bus and observe a crash

**Azure TRE release version (e.g. v0.14.0 or main):**
main
**Deployed Azure TRE components - click the (i) in the UI:**
