Fixing streaming by migrating to Typhoeus

[gbaptista]

• Fixes Streaming is not working #11
• Adds Typhoeus as the default Faraday adapter.

New option to customize Faraday adapter:

require 'faraday/net_http'

client = Gemini.new(
  credentials: { service: 'vertex-ai-api', region: 'us-east4' },
  options: {
    model: 'gemini-pro',
    connection: { adapter: :net_http }
  }
)

New option to set service version:

client = Gemini.new(
  credentials: {
    service: 'generative-language-api',
    api_key: ENV['GOOGLE_API_KEY'],
    version: 'v1beta'
  },
  options: { model: 'gemini-pro', server_sent_events: true }
)

Why is Typhoeus the default rather than being used only for streaming with server-sent events?
I prefer using a single adapter for all use cases to ensure a consistent experience across different scenarios, e.g., to avoid having different timeout behaviors due to an unknown change of adapters under the hood. But, users can still choose another adapter if they want to.

Why Typhoeus?
Faraday's default adapter (Net::HTTP), specifically for the peculiar way that Google implements streaming in their APIs, is not capable of actually streaming data. We need an adapter with support for Response Streaming + Parallel Requests, which leads to the following options:

• Async::HTTP::Faraday
• Typhoeus
• httpx

async-http adds async, which feels like adding an extra layer of dependency and potential complexity (Async do) unnecessary to the gem.

httpx seems promising, but for some reason, it does not work out of the box for the purpose of understanding Google's particular way of streaming.

Typhoeus just works out of the box, backed by libcurl that is something widely available and supported. Both timeouts and image/video modes work as expected.