fix(transport): Make server builder more consitient

[jdahlq]

Motivation

See Issue #900

Solution

See Issue #900

[jdahlq]

I guess this might cause a silent breakage for code like this:

let router = Server::builder();
router.timeout(Duration::from_secs(10));

router.timeout would no longer do anything if not chained or reassigned. We could add a #[must_use] annotation (and probably should add it for all these functions which return Self), which presumably would cause a compiler error for users with such code. Not sure what the best course of action is, here.

[LucioFranco]

Yeah I think adding must use makes sense here then. If you want to go ahead and add that change here as well we can merge this.

[jdahlq]

Done.

[LucioFranco]

Can you rebase against master? I fixed the ci failure #914

[jdahlq]

Thanks, rebased.