asynchronous web/api authorize filter calls

[sventhiel]

Description
With regard to the preferred use of async methods, I tried out if it will work for both filters, BExISApiAuthorizeAttribute.cs and BExISAuthorizeAttribute.cs to perform the call "OnAuthorization" asynchronously. At the first sight, it seemed to work, but soon first issues came up. At the end, within MVC (regardless if MVC4 or MVC5) it is not possible and furthermore not a good idea to perform such calls in an asynchronous manner.

Sources:
Can we make async method call from MVC filter?

Conclusion
Even after small refactoring of the existing attributes and authorize calls, we will stick to synchronous execution.