Add option for noRedirect to serve UI directly at the route prefix

[jdhollander]

This PR is related to #117. I like the suggestion, and it would be beneficial to me to have this feature, so I've implemented it.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

noRedirect option

I have introduced a new option, which will disable the redirect to /static/index.html for the documentation UI. On visiting the documentation route, the UI is returned without redirection, and the url stays clean.

await fastify.register(require('@fastify/swagger-ui'), {
  routePrefix: '/documentation',
  noRedirect: true,
})

[Uzlopak]

noRedirect is not about not redirecting but actually about some routing option. This seems kind of wrong.

[jdhollander]

noRedirect is not about not redirecting but actually about some routing option. This seems kind of wrong.

Thanks for the feedback. Any suggestion on what I should call it? serveIndexAtRootPrefix? noStaticIndexRedirect?

Otherwise, is the general approach to this ok?

[Uzlopak]

Why do we even redirect? I have unfortunately currently no motivation to deep dive into the topic. But maybe not redirecting but directly serving the expected files should be the desired result?

Maybe related to
fastify/fastify-swagger#39
fastify/fastify-swagger#56
fastify/fastify-swagger#65

[mcollina]

I did the redirect because I was too lazy to figure out how to make that rendering work correctly. At the beginning, the HTML was entirely static, so just redirecting it makes sense.

Maybe we should flip it to true by default.