Webapi-Swagger : Keep track of all errors and report them at the end instead of failing abruptly

[kahlil29]

Currently we error out the program in a lot of places where we encounter unexpected values or situations.
Instead of this, we need to collect all the errors (via State) and output them at the end of generation.

As discussed with @ersran9 , an alternative way of doing this would be in the mtl style with Validations, but since we already have the State monad in a lot of our core functions, it should be relatively easier to implement by extending the state to a tuple containing already existing [CreateNewType] so that it would end up becoming
([CreateNewType], [ErrMsg])

[kahlil29]

Note : The type ErrMsg would be a sum-type consisting of the classes of possible errors that we could encounter.