Function `_http_view_func_wrapper` should use `@functools.wraps`

[svleeuwen]

For example when using Flask-Talisman you can specify per-view options using:

@functions_framework.http
@talisman(content_security_policy=None)
def foo(request):
    ...

Talisman will decorate the view function with a talisman_view_options attribute which is retrieved later like this:

view_options = getattr(view_function, 'talisman_view_options', {})

Adding functools.wraps makes sure all function attributes are copied from the original function to the _http_view_func_wrapper.

Will create a pull request for this in a minute.

[anniefu]

Hello, thanks for filing this issue!

This seems like a good change to add. Would it be possible for you to add a unit test and open a PR?

[svleeuwen]

@anniefu added test to PR

[anniefu]

Fixed with #179