drop support of passing prefix to .middleware/.legacyMiddleware

[tunnckoCore]

Basically it works correctly. But later if you wanna list them all you can't get correct and actual routes.

If you have, for example, one router and use .middleware multiple times with different prefixes all will work, but you can't get all available routes - they works, but you can list them for example, after the server is started (for example list them from the app.listen(port, fn) callback)

let Router = require('koa-rest-router')
let router = Router()

router.resource('users').resource('cats')

let Koa = require('koa')
let app = new Koa()

app.use(router.middleware())
app.use(router.middleware({ prefix: '/api/v1' }))
app.use(router.middleware({ prefix: '/foo/api/v3' }))

router.routes.forEach((route, idx) => {
  console.log(idx + 1, route.path)
})

It will print only 14 routes, only these that are on / prefix, but not the others. They will work. If you access them through web. You will have 42 actual and working routes, but it will output only 14 of them.

So if you wanna do the trick correctly you should do 3 different routers and use the .extend method.

let router2 = Router({ prefix: '/api/v1' })
let router3 = Router({ prefix: '/foo/api/v3' })

// add `router`'s routes on `router2`
router2.extend(router)

// add `router`'s routes on `router3`
router3.extend(router)

// add the three routers on koa server
app.use(router.middleware())
app.use(router2.middleware())
app.use(router3.middleware())

let i = 1

router.routes.forEach((route) => console.log(i++, route.path))
router2.routes.forEach((route) => console.log(i++, route.path))
router3.routes.forEach((route) => console.log(i++, route.path))