Fixing req and payload

[DeliciousBounty]

Hey Raz,
Here two majors things:

• Added to the function "create payload" the possibility to create also payload for POST request. I updated the in all POST request.
• Added the possiblity to construct a server URI from OAS server object with placeholder ( filename: req.rs)

[RazMag]

im merging this but I need to implement the use of the new URI function.
but first Ill need to add support for 'server' input in from config/command line.
After that ill rewrite all the tests to use the new URI function