Reconsider regex for URL scheme

[adatzer]

Describe the bug

Currently this regex is used to validate the protocol scheme. This means that a protocol like safari-web-extention will become null.

This can result in unexpected behaviour for setCustomUrl, if it is called with a url whose protocol does not conform to this regex. In that case, the url argument gets appended to base url.

To Reproduce

Example for JavaScript tracker, setup the tracker and call:

snowplow('setCustomUrl', 'safari-web-extention://whatever.com');

Expected behavior

That setCustomUrl sets the url to its argument independent of protocol scheme.

Additional context

• Currently the page_urlscheme is also a Snowplow atomic property, whose current max length is 16, which results in events getting invalidated if their page url has a protocol longer than that.
• See also: RFC 2396 Scheme Component