Add Faraday 1.x examples in authentication.md docs

Fixes #1317
Fixes #1314

docs/middleware/request/authentication.md

@@ -11,6 +11,8 @@ top_link: ./list
 
 The `Faraday::Request::Authorization` middleware allows you to automatically add an `Authorization` header
 to your requests. It also features a handy helper to manage Basic authentication.
+Please note the way you use this middleware in Faraday 1.x is different,
+examples are available at the bottom of this page.
 
 ```ruby
 Faraday.new(...) do |conn|
@@ -37,3 +39,28 @@ Faraday.new(...) do |conn|
   conn.request :authorization, :basic, 'username', 'password'
 end
 ```
+
+### Faraday 1.x usage
+
+In Faraday 1.x, the way you use this middleware is slightly different:
+
+```ruby
+# Basic Auth request
+# Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=
+Faraday.new(...) do |conn|
+  conn.request :basic_auth, 'username', 'password'
+end
+
+# Token Auth request
+# `options` are automatically converted into `key=value` format
+# Authorization: Token authentication-token <options>
+Faraday.new(...) do |conn|
+  conn.request :token_auth, 'authentication-token', **options
+end
+
+# Generic Auth Request
+# Authorization: Bearer authentication-token
+Faraday.new(...) do |conn|
+  conn.request :authorization, 'Bearer', 'authentication-token'
+end
+```