Proxy implementation that allows modification of the traffic from and to the samples for testing purposes.
The proxy has two modes - one that simply forwards the traffic and one which allows us to modify the requests and responses coming and going through the proxy, using Man-In-The-Middle (MITM).
A POST request to the /session endpoint starts a MITM session. The body of the
request should contain JSON document with modifyUrl property. This property
is the URL where the proxy will redirect all traffic until the session is
stopped. A DELETE request to the /session endpoint stops the session.