add support for a route() helper to get fully qualified URLs of HTTP endpoints at runtime

For HTTP endpoints declared via @endpoint like so:

  @endpoint({ get: '/assets/{assetName}' })
  async myMethod(assetName: string) {
    ....
  }

It would be great to have a helper function to obtain the fully qualified URL of such an endpoint - incl. domain/hostname of the golem deployment. The existing createWebhook() helper already returns a FQ URL.

Ideally the helper function should support:

• generating FQ urls (ie. http://mygolemhost.com/assets/myasset)
• absolute URLs without hostname (ie. /assets/myasset)
• a flag to control if https or http will get get returned

The helper method must be able to accept (and validate) named route args for both: path and query args.

Immediate use cases:

• serving assets and rendering these URLs in templates / html
• sending out signup / confirmation links via email

Start by examining the existing createWebhook() helper and the @endpoint declarations described in the issue. Define the helper's behavior for fully qualified and hostname-free URLs, HTTP versus HTTPS, and validated path and query arguments; done means all listed URL forms and immediate use cases are supported.