* read cookie while initialising websocket connection (fix#1660)
* add tests for cookie on websocket init
* fix logic for tests
* enforce cors, and flag to force read cookie when cors disabled
- as browsers don't enforce SOP on websockets, we enforce CORS policy
on websocket handshake
- if CORS is disabled, by default cookie is not read (because XSS
risk!). Add special flag to force override this behaviour
* add log and forward origin header to webhook
- add log notice when cors is disabled, and cookie is not read on
websocket handshake
- forward origin header to webhook in POST mode. So that when CORS is
disabled, webhook can also enforce CORS independently.
* add docs, and forward all client headers to webhook
