Avoid monkey patching the multipart-post gem to specify Content-Type headers

README.md

@@ -75,8 +75,6 @@ The above options allow you to change the endpoint (to be able to hit the produc
 
 The docusign\_rest gem makes creating multipart POST (aka file upload) requests to the DocuSign REST API dead simple. It's built on top of Net:HTTP and utilizes the [multipart-post](https://github.com/nicksieger/multipart-post) gem to assist with formatting the multipart requests. The DocuSign REST API requires that all files be embedded as JSON directly in the request body (not the body\_stream like multipart-post does by default) so the docusign\_rest gem takes care of [setting that up for you](https://github.com/j2fly/docusign_rest/blob/master/lib/docusign_rest/client.rb#L397). 
 
-This gem also monkey patches one small part of multipart-post to inject some header values and formatting that DocuSign requires. If you would like to see the monkey patched code please take a look at [lib/multipart-post/parts.rb](https://github.com/j2fly/docusign_rest/blob/master/lib/multipart_post/parts.rb). It's only re-opening one method, but feel free to make sure you understand that code if it concerns you. 
-
 ### Examples
 
 * These examples assume you have already run the `docusign_rest:generate_config` rake task and have the configure block properly setup in an initializer with your username, password, integrator\_key, and account\_id. 

lib/docusign_rest.rb

@@ -4,7 +4,6 @@
 require_relative 'docusign_rest/utility'
 require 'multipart_post' #require the multipart-post gem itself
 require 'net/http/post/multipart' #require the multipart-post net/http/post/multipart monkey patch
-require_relative 'multipart_post/parts' #require my monkey patched parts.rb which adjusts the build_part method
 require 'net/http'
 require 'json'
 

lib/docusign_rest/client.rb

@@ -547,6 +547,9 @@ def initialize_net_http_multipart_post_request(uri, post_body, file_params, head
       # headers={} - The fully merged, final request headers
       # boundary   - Optional: you can give the request a custom boundary
       #
+
+      headers = headers.dup.merge(parts: {post_body: {'Content-Type' => 'application/json'}})
+
       request = Net::HTTP::Post::Multipart.new(
         uri.request_uri,
         { post_body: post_body }.merge(file_params),