Add URL

[xelahalo]

I made this draft so that we can continue our discussion on the URL or ParameterizedWebURL. There are a few to things to discuss:

• validation of a URL (either in-built or caller defined)
• support for custom schemes ( like a deep link to a smartphone based study)
• creating support for parameterization of a url, such as in WebTask

Seems like a bigger task, should I create an issue instead?

[Whathecode]

Based on my last analysis, it seemed like there was no real potential reuse for URL validation: it couldn't be used by WebTask, since that needs to take the special "parameterized" syntax into account.

But, there is some potential reuse for a ParameterizedWebURL, including validation of the URL, and embedded parameters. Maybe generic, with an enum as type parameter which determines the parameters. And, which is URL-encoding aware, which will become relevant for "device role".

Static typing of URL in a WebsiteDeviceRegistration would be a "nice to have", but is different from the above, and the above sounds more relevant to me. I could have a go maybe this weekend. :)

support for custom schemes ( like a deep link to a smartphone based study)

This sounds like potentially yet another use case. It sounds like it makes more sense to consider the specific use cases where a URL is used (or composed) and create custom validation for those. E.g., configuring a WebsiteDeviceRegistration with a smartphone deep link is nonesensical, and you'd want the more strict http/https.

Lastly, I think we can easily add this later without impacting the web API. I don't think this is type information which is relevant to serialize, so a "primitive serializer" would be used to serialize it as plain strings either way.

[Whathecode]

Closed as it sounds like the other parts of this PR which weren't merged need more clarity in terms of what they hope to achieve.