Custom query parameter without value doesn't work.

[tricki]

I tried to use a custom query string of ?foo (with a name but no value) but when I query it using GraphQL all parameters without a value get removed, even if I also add a hash (e.g. ?foo&bar=1#hash becomes ?bar=1#hash).

I believe the problem comes from the Url::getQuery() method defined in the utils package: https://github.com/sebastian-lenz/craft-utils/blob/main/src/models/Url.php#L136-L139

From my reading of RFC 3986 I don't see that a value is required. It does say this which implies that it's optional:

However, as query components are often used to carry identifying information in the form of "key=value" pairs [...]