Traditionally javax.servlet.Filter services were picked up by the Sling
Main Servlet and used as filters regardless of any service registration
properties. The filter.scope property could optionally be used to define
a scope for the filter (request or component before SLING-1213, now also
INCLUDE, FORWARD, and ERROR).
To not pick up filters destined for the Apache Felix Http Service
(registered with the "pattern" service property) we explicitly xclude those.
I would like to go a step further and ....
* define a new service property sling.filter.scope
* deprecate the old filter.scope property
* require services to either have the sling.filter.scope or
the filter.scope (backwards compatibility) property set
* optionally: support for a configuration option to cause
filters without a scope property to still be picked up
I consider renaming the official name to prevent any name collisions.