HTTPService's Self should be mutable to maintain state over incoming requests

[saviorand]

Issue raised by the author of https://github.com/alainrollejr/mocodes

Is your feature request related to a problem? Please describe. There is currently no way maintain internal state over incoming requests

Describe the solution you'd like It should be allowed to change self on the HTTPService .

Describe alternatives you've considered Currently the issue can be solved using pointers, but it's a better experience if self can be mutated and the user does not have to resort to pointers.