Docs: Remove extra underscore from function header

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Add event context accessors

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Docs: Indicate that stream event context is sampled on event append

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add event context accessors unit tests

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>