When I writing 'ndp_proxy' service plugin, I found I couldn't get enough
informations about router from the callback system (Such as: the origin
request body of user send). So, for write service plugin that related
router plugin more concisely I commit this patch.
This patch proposal two changes about router callback publish events:
1. Add 'request_body' parameter to some event's payload
2. add 'BEFORE_UPDATE' event for router gateway
Related-bug: #1877301
Change-Id: I5f6a4e6f0b7c5feb794ddb7efbd07d01bad91af8
e4c168b1fc