Add asStream support

[delvedor]

With this option, the transport will return a readable stream directly from the HTTP layer, it won't try to parse it or decompress it.
The response size check won't be executed.

import { Readable } from 'stream'
import {
  Transport,
  WeightedConnectionPool,
  UndiciConnection
} from '@elastic/transport'

const pool = new WeightedConnectionPool({ Connection: UndiciConnection })
pool.addConnection('http://localhost:9200')
const transport = new Transport({ connectionPool: pool })

const body = await transport.request<Readable>({
  method: 'GET',
  path: '/'
}, {
  asStream: true
})

body.setEncoding('utf8')
let payload = ''
for await (const chunk of body) {
  payload += chunk
}
console.log(payload)

Closes: elastic/elasticsearch-js#1597

[delvedor]

cc @mshustov @pgayvallet now we are exporting the TransportOptions as well! 🎉

[mshustov]

Doesn't it mean that we need to re-generate all the API type definitions?

[delvedor]

Nope, the connection.request is only used by the transport, and its signature hasn't changed.
In the client you might need to use directly client.transport.request<Readable>, as the surface API assumes you are using JSON.