Consider implementing PSR-7 & PSR-15

[rahmanramsi]

With implementing PSR-7 & PSR-15, this will allow application to be running on new runtime (Swoole, RoadRunner, FrankenPHP, etc).
The application will gain a huge performance boost with this implementation.

[asmecher]

@rahmanramsi, I support this, but the path to reaching PSR-7 and PSR-15 compliance will definitely be to continue moving OJS into a Laravel platform. We have recently moved API request handling over to Laravel, for example, and starting with 3.5 session management is migrated too. We're gradually replacing the old homebrew app stack with Laravel, and that'll give us PSR-7 and PSR-15 in the process.