[Bug] `validate` should check passed in model type

[Pirulax]

Describe the bug
The validate function should check the type of the passed in schema.
In my case doing this:

import sanic as s
from sanic_ext import validate

class MyRESTMethodArgs:
    id : str
@bp.post('/create')
@validate(json=MyRESTMethodArgs)
async def post_create(req : s.Request, body : MyRESTMethodArgs):
    pass # Business logic

Fails miserably with:

File "<irrelevant>\.venv\Lib\site-packages\sanic_ext\extras\validation\decorator.py", line 73, in decorated_function
    retval = f(*args, **kwargs)

Inspecting it closer, it turns out schemas looks like this:

{'json': {}, 'form': None, 'query': None}

I assume the issue is with generate_schema for some reason just returning {} instead of raising an exception

To Reproduce
See above

Expected behavior
validate should fail if it encounters a schema model it can't process (As according to the docs, a simple Python class can't be used)

Environment (please complete the following information):
mode: debug, single worker
server: sanic, HTTP/1.1
python: 3.12.4
platform: Windows-11-10.0.22631-SP0
packages: sanic-routing==23.12.0, sanic-ext==23.12.0

Yeah this behaviour checks out looking at internal make_schema function:

sanic-ext/sanic_ext/extras/validation/schema.py

Lines 41 to 69 in fd85ada

	def make_schema(agg, item):
	if type(item) in (bool, str, int, float):
	return agg
	if is_generic(item) and (args := get_args(item)):
	for arg in args:
	make_schema(agg, arg)
	elif item.__name__ not in agg and (
	is_dataclass(item) or is_attrs(item) or is_msgspec(item)
	):
	if is_dataclass(item):
	fields = item.__dataclass_fields__
	elif is_msgspec(item):
	fields = {f.name: f.type for f in msgspec_type_info(item).fields}
	else:
	fields = {attr.name: attr for attr in item.__attrs_attrs__}
	sig = signature(item)
	hints = parse_hints(get_type_hints(item), fields)
	agg[item.__name__] = {
	"sig": sig,
	"hints": hints,
	}
	for hint in hints.values():
	make_schema(agg, hint.hint)
	return agg

That is, passing a bare python class will not raise error but return the empty dict.

validate should fail if it encounters a schema model it can't process (As according to the docs, a simple Python class can't be used)

I think only pydantic, msgspec, attrs and dataclasses are supported

We can add a check here

sanic-ext/sanic_ext/extras/validation/setup.py

Lines 48 to 55 in fd85ada

	def generate_schema(param):
	try:
	if param is None or is_msgspec(param) or is_pydantic(param):
	return param
	except TypeError:
	...
	return make_schema({}, param) if isclass(param) else param

maybe like

+ if isclass(param) and not is_attrs(param) and not is_dataclass(param):
+       raise SchemaNotSupported

return make_schema({}, param) if isclass(param) else param