Authorization based on the username of Basci Auth schema

[zhaohuabing]

Description:

Support authorization based on the username of the Basic Auth schema within the SecurityPolicy.

Envoy Gateway currently supports authn with Basic Auth, the username can be extracted and put into metadata, then used as a subject for authz.

Depends on Envoy issues:

• BasicAuth HTTP filter: emit metadata containing username envoy#34797
• Support metadata input in Mathching API envoy#34092

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.