Add a helper to add a beta version (#1343)

* Add a helper to add a beta header

* Typo

lib/stripe.rb

@@ -121,6 +121,14 @@ def self.set_app_info(name, partner_id: nil, url: nil, version: nil)
     }
   end
 
+  def self.add_beta_version(beta_name, version)
+    if api_version.include?("; #{beta_name}=")
+      raise "Stripe version header #{api_version} already contains entry for beta #{beta_name}"
+    end
+
+    self.api_version = "#{api_version}; #{beta_name}=#{version}"
+  end
+
   class Preview
     def self._get_default_opts(opts)
       { api_mode: :preview }.merge(opts)

test/stripe_test.rb

@@ -119,6 +119,18 @@ class StripeTest < Test::Unit::TestCase
       assert_equal "2018-02-28", Stripe.api_version
     end
 
+    should "allow beta versions to be added once only" do
+      Stripe.api_version = "2018-02-28"
+
+      Stripe.add_beta_version("my_beta", "v2")
+      assert_equal "2018-02-28; my_beta=v2", Stripe.api_version
+
+      err = assert_raises do
+        Stripe.add_beta_version("my_beta", "v1")
+        assert_equal(err, "Stripe version header 2018-02-28; my_beta=v2 already contains entry for beta my_beta")
+      end
+    end
+
     should "allow connect_base to be configured" do
       Stripe.connect_base = "https://other.stripe.com"
       assert_equal "https://other.stripe.com", Stripe.connect_base