fix(web): add exception handling

[amit-nagish]

when making an incorrect request, i want to see a json response, not an HTML.

For example, I ran http://127.0.0.1:8000/lexicons/omw-en:1.4/words/bass (which is wrong, should have done ?form=bass) and it gave me an HTML error rather than JSON

[goodmami]

Thanks @amit-nagish, this issue does look like an oversight. I probably assumed that the response body didn't matter much if the status was not 200, but what you have here looks much better. I might have more to say once I get a chance to properly review it.

[amit-nagish]

Hi @goodmami ! did you get a chance to take a closer look?

I have a bunch of updates to the web server in my fork / locally that I believe improve the experience, and would love to contribute them one by one

[goodmami]

did you get a chance to take a closer look?

I'm currently traveling, which is why I'm being slow to respond. I hope to have some more time to review in the coming days. Thanks for your patience.

[goodmami]

Mostly looks good. I just have some style suggestions.

Also instead of making calls with dicts like this:

some_function({
    "key": val,
}, keyword=xyz)

Let's try to be more compliant with code formatting tools like Ruff/Black:

some_function(
    {
        "key": val,
    },
    keyword=xyz,
)

[goodmami]

This is recreating getattr behavior:

Suggested change

	status_code = exc.status_code if hasattr(exc, 'status_code') else 500
	status_code = getattr(exc, 'status_code', 500)

[goodmami]

This could also be a getattr call. There's a case for leaving it as an inline conditional if str(exc) is something you don't want to call unless it's needed, but I don't think that's a big concern here.

[goodmami]

Maybe add this above at the end of the "Exception handlers" section of the code:

exception_handlers = {
    HTTPException: http_exception_handler,
    wn.Error: http_exception_handler,
    Exception: http_exception_handler,
}

Then simplify this line as follows:

Suggested change

	app = Starlette(debug=True, routes=routes, exception_handlers={
	HTTPException: http_exception_handler,
	wn.Error: http_exception_handler,
	Exception: http_exception_handler,
	})
	app = Starlette(debug=True, routes=routes, exception_handlers=exception_handlers)