Add functional version of the middleware that changes the default query based on request body

• The middleware is on src/middlewares/reqBody.js
• It has the methods parse and add_metrics
• The method parse processes the body of the HTTP request and calls a method based on its mode. Currently, it only supports the mode add_metrics
• If the mode is add_metrics, it calls the method add_metrics for each column and its specified operations
• The method add_metrics adds a field to req.sql for each operation specified to the column and sets the flag req.hasMetrics to true, so that the route knows that it should not create its default query