4 Fixes on Calling Cloud Flows from Power Pages

[Kunter-Bunt]

1. The changes in 961d54b are a clear mistake because the default contentType of ajax is formData. Readded the contentType.
   
2. When you pass the parameters wrong, PowerPages also refuses to pass the default parameters siteID, siteUrl and userId. It is therefore detrimental that the guidance on no parameter says to pass an empty payload while you should pass an empty eventData.
   
3. The HTTP Request sample passes the Location Parameter directly, not wrapping it in eventData. This is clearly contradicted by all the other documentation and does not work in my testing.
4. While inputs are passed case sensitive, the outputs are passed back in lowercase. Added a note for that. (Technically you can see that in the tutorial, but its spaced far apart and is easily overlooked)
   

[Kunter-Bunt]

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