Add comment explaining why we call a synchronous method

... only from an asynchronous context.

Signed-off-by: Brian Upton <brian.upton@broadcom.com>

src/bosh-monitor/lib/bosh/monitor/plugins/pagerduty.rb

@@ -34,6 +34,11 @@ def process(event)
 
  request[:proxy] = options['http_proxy'] if options['http_proxy']
 
+ # Note this appears to be the only use of `#send_http_post_request_synchronous_with_tls_verify_peer` from git
+ # history it appears that the previous asynchronous implementation (EventMachine) was not able to use
+ # TLS-proxies, so a synchronous call was made from asynchronously.
+ # This should probably be re-implemented to use the asynchronous `HttpRequestHelper#send_http_post_request`
+ # method _however_ that method should be updated to use `OpenSSL::SSL::VERIFY_PEER`.
  Async do
  send_http_post_request_synchronous_with_tls_verify_peer(API_URI, request)
  rescue StandardError => e