fix issue with react client post/put to drafts_controller.rb

[briri]

Hey @andrewebdev. There were some issues with the way the POST/PUT data was being sent to Rails.

First, the api.js had a hard coded header of Content-Type: application/x-www-form-urlencoded but the pages were sending JSON. This was causing Rails to not be able to interpret the body correctly. I discovered that we can just exclude that header and Rails will apparently figure it out for us.

I referenced this article to figure out what to do on the React side.

Second, Rails controllers have normally expect every form element to include a name and id. For example id="plan_title" name="plan[title]" and then Rails gets these as nested parameters plan: { title: 'value' }. I wasn't sure how to structure that properly in React though (I suspect that we might need to encode the name due to the brackets). Since I couldn't get the dmp[title] to work, I just removed the need for the top level 'dmp' completely.

Please feel free to modify any of the React JS changes.

• Removed the need for the React client to nest all fields under the top level dmp (e.g. send { title: 'foo' } instead of { dmp: { title: 'foo' } }
• Commented out the React client's Content-Type header. Rails figures out what is being sent
• Commented out the call to api.getFileDataURL in new.js. Rails was able to work with the File as it was sent via formData
• Updated the new.js file so that the form fields match what is being sent back to rails so we can just send formData
• Added 'dmproadmap_opportunity_number' to the Rails list of acceptable parameters
• Updated cors config to allow a preflight 'options' request (although I don't think this was necessary)

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