Drop invalid client hints

[adatzer]

The client hints schema used follows exactly the User-Agent Client Hints interface specification.

The JS tracker, in order to attach the client hints entity, currently checks whether userAgentData is there, i.e. whether the API is implemented. However this means that user-agents who have implemented the API, but have not done so according to the spec, create invalid events, which however represent valid user behaviour.

Expected behavior

The JS tracker checks, at least briefly, the compliance of the implemented client-hints API before attaching the context entity to the event. If it finds that the user-agent is not compliant, it does not attach the client-hints context, i.e. an inaccurate implementation of the user-agent client hints interface has the same outcome as no implementation of it.

Example of invalid user-agent client hints:

{
    "brands": [
        {
            "brand": "Opera GX",
            "version": 98
        }
    ]
}