Consider promoting well known http headers to attributes

[mandarjog]

Mixer configuration system enforces type safety at config ingestion time. The effectiveness of the type checks depend on having typed attributes. Isio vocabulary defines a set of typed attributes.

However request.header ( map <string, string> ) contains a lot of information in untyped, string form. This compromises the effectiveness of the type system.

Consider promoting headers to typed attributes referer header to attribute type URI (instead of string, which it is today) From header to attribute type EMAIL X-Forwarded-Host DNS_NAME etc

This also has efficiency benefit on the wire.

[kyessenov]

These are loose web standards. What happens if the headers are mal-typed?