typescript-fetch: support runtime parsing

[mnahkies]

currently only the typescript-koa does any runtime parsing/validation.

add support to the typescript-fetch template for validating parameters, and parsing responses using the configured schema builder (ie: zoa / joi)

[paztis]

with --enable-runtime-response-validation we can add the response parsing, but there's no way to manage the fetch parameters validation before sending the fetch

[mnahkies]

I'm (somewhat) open to opinions on this, but my current thinking is that it isn't necessary to client side (runtime) validate the request parameters - the server should be the source of truth for runtime parameter validation.

We endeavour to provide accurate build time validation through strong types, but I wouldn't want a mistake in the validation to prevent a valid request being submitted, and if the server isn't correctly validating it's inputs that's a big issue that shouldn't be papered over by client side validation. Maybe there's an argument for avoiding invalid requests but I've not come across a strong use case for this, normally you'll do your client side validation over things like form inputs prior to getting near an API client.