This commit adds functionality of sending webhook notifications to
various projects that require keystone authentications. For which user
need to set auth credentials in conf under keystone header.
By default it is disabled, which can be enabled in conf.
Change-Id: I3e773af8c3ebe0cf1d57e8fa1351b1e725a9cfa0
Partially-Implements: blueprint add-monasca-push-driver
Story: 2003105
Task: 23220