Feature : add a way to agregate all swagger from function in one exposed by SlimFaas.

[guillaume-chervet]

SlimFaas should be able to aggregate swagger from all is referenced functions.

Aggregation should de dynamic at execution time.
If a function is not started it should started in order to fetch its swagger.json file from v3 specification.

New annotation to declare swagger of a function.

SlimFaas/Swagger: "swagger.json"
// path to the swagger file
Defaut if empty and no swagger will be retrieved

For exemple we can access to a pod by his name :

http://localhost:30021/function/fibonacci1/hello/guillaume
http://localhost:30021/function/fibonacci2/hello/elodie
http://localhost:30021/function/fibonacci3/hello/julie

I would like to merge swagger files :

http://localhost:30021/function/fibonacci1/swagger.json
http://localhost:30021/function/fibonacci2/swagger.json
http://localhost:30021/function/fibonacci3/swagger.json

In one created dynamicaly from SlimFaas:
http://localhost:30021/swagger.json