feat: Add Twilio::HTTP::Client#configure_connection (#559)

Co-authored-by: Darwin Carrillo <darwin.carrillo@shopify.com>
Co-authored-by: Adam Archibald <adam.archibald@shopify.com>
Co-authored-by: Sam Bostock <sam.bostock@shopify.com>

README.md

@@ -158,6 +158,14 @@ message_sid = 'SMxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
 
 To use a custom HTTP client with this helper library, please see the [Twilio documentation](https://www.twilio.com/docs/libraries/ruby/custom-http-clients).
 
+To apply customizations such as middleware, you can use the `configure_connection` method like so:
+
+```ruby
+@client.http_client.configure_connection do |faraday|
+  faraday.use SomeMiddleware
+end
+```
+
 ### Handling Errors
 
 ```ruby

lib/twilio-ruby/http/http_client.rb

@@ -16,18 +16,28 @@ def initialize(proxy_prot = nil, proxy_addr = nil, proxy_port = nil, proxy_user
         @ssl_ca_file = ssl_ca_file
         @timeout = timeout
         @adapter = Faraday.default_adapter
+        @configure_connection_blocks = []
+      end
+
+      def configure_connection(&block)
+        raise ArgumentError, "#{__method__} must be given a block!" unless block_given?
+
+        @configure_connection_blocks << block
+        nil
       end
 
       def _request(request)
         @connection = Faraday.new(url: request.host + ':' + request.port.to_s, ssl: { verify: true }) do |f|
           f.options.params_encoder = Faraday::FlatParamsEncoder
           f.request :url_encoded
-          f.adapter @adapter
           f.headers = request.headers
           f.basic_auth(request.auth[0], request.auth[1])
           f.proxy = "#{@proxy_prot}://#{@proxy_auth}#{@proxy_path}" if @proxy_prot && @proxy_path
           f.options.open_timeout = request.timeout || @timeout
           f.options.timeout = request.timeout || @timeout
+
+          @configure_connection_blocks.each { |block| block.call(f) }
+          f.adapter @adapter
         end
 
         @last_request = request

spec/http/http_client_spec.rb

@@ -6,6 +6,29 @@
     @client = Twilio::HTTP::Client.new
   end
 
+  it 'should allow adding a request configuration block' do
+    @client = Twilio::HTTP::Client.new
+    @connection = Faraday::Connection.new
+
+    blocks_spy = spy('blocks')
+
+    @client.configure_connection do |f|
+      blocks_spy.first_block_called(f)
+    end
+
+    @client.configure_connection do |f|
+      blocks_spy.second_block_called(f)
+    end
+
+    expect(Faraday).to receive(:new).and_yield(@connection).and_return(@connection)
+    allow_any_instance_of(Faraday::Connection).to receive(:send).and_return(double('response', status: 301, body: {}, headers: {}))
+
+    @client.request('host', 'port', 'GET', 'url', nil, nil, {}, ['a', 'b'])
+
+    expect(blocks_spy).to have_received(:first_block_called).with(@connection)
+    expect(blocks_spy).to have_received(:second_block_called).with(@connection)
+  end
+
   it 'should allow setting a global timeout' do
     @client = Twilio::HTTP::Client.new(timeout: 10)
     @connection = Faraday::Connection.new