New option `application` to allow developers to use their custom server application

[snitin315]

Feature Proposal

New option application: { type: "connect", options: ...options } (default value is express)

Feature Use Case

we need application: { type: "connect", options: ...options } (default value is express) in the long term we should migrate on connect or maybe something more simple, express is not get updated a long time, but we need to support http2/https without any problems and workarounds, I think now we can setup our tests and fix code for connect and them add this options, so we can have two-three PRs

Please refer #4068 (comment)

[alexander-akait]

Let's close in favor of #4741 (there are more comments)