Tracking issue: Blog post for 1.9 release

[jonasrosland]

This is a tracking issue (as discussed in the community meeting) to ensure we have a blog going out together with the 1.9 release, explaining new features and functionality.

• Assigned blog author
• Blog drafted
• Blog reviewed
• Blog published

[youngnick]

Features that will need documentation:

• external auth (Provide support for integrating with an external auth service. #432)
• status changes (design: Add a pattern for adding extensible status information to HTTPProxy #2495)
• CRD v1 (pr examples: generate v1 CustomResourceDefinitions #2916)
• go-control-plane experimental support (Replace GRPC server with envoy's go-control-plane #2134 )