Resolve "Error handling on send"

Closes #9 (closed)

features/adapter_publish.feature

     When a mock send API response is configured to return an error
     When the publish method is called
     Then an error response is returned with status 403
+
+  Scenario: On 403 the message is retried once with new credentials 
+    Given valid config 
+    When the adapter instance is created 
+    When the auth method is called 
+    When a mock send API response is configured to return an error 
+    When the publish method is called 
+    Then an error response is returned with status 403 
+    Then the credentials are deleted
+    Then the publish method is called with is_retry on
+    Then the getAuthorizationHeader method is called 
+    
+  Scenario: On a retried 403 the message is not retried again
+    Given valid config 
+    When the adapter instance is created 
+    When the auth method is called 
+    When a mock send API response is configured to return an error 
+    When the publish method is called with is_retry on
+    Then an error response is returned with status 403
+    Then the credentials are deleted 
+    Then the publish method is not called again