Show url trace

[simonfrey]

It could be of interest for the user to see the complete redirect trace of the shortlink (if it redirected via different other services for example) e.g.

1. bit.ly/de
2. boma.de/dasd
3. trackmealot.com/askdma
4. heise.de

This should be hidden behind a "Show trace" button in the front end to keep the UI simple.

I assume this is only about 1h of work to bubble the info into the UI and save it into the DB as the redirect loop is already done. Good issue for getting familiar with the code base and learning about the golang http.Client.

An article that could help: https://jonathanmh.com/tracing-preventing-http-redirects-golang/