actix-web: v4.0.0-beta.1

Added

• Compat middleware enabling generic response body/error type of middlewares like Logger and
  Compress to be used in middleware::Condition and Resource, Scope services. #1865

Changed

• Update actix-* dependencies to tokio 1.0 based versions. #1813
• Bumped rand to 0.8.
• Update rust-tls to 0.19. #1813
• Rename Handler to HandlerService and rename Factory to Handler. #1852
• The default TrailingSlash is now Trim, in line with existing documentation. See migration
  guide for implications. #1875
• Rename DefaultHeaders::{content_type => add_content_type}. #1875
• MSRV is now 1.46.0.

Fixed

• Added the underlying parse error to test::read_body_json's panic message. #1812

Removed

• Public modules middleware::{normalize, err_handlers}. All necessary middleware structs are now
  exposed directly by the middleware module.