Add URL shortening

[hathix]

Our URLs for specific routes & trips are getting pretty long, e.g. "https://muni.opentransit.city/route/41/direction/41___I_F00/fromStop/6769/toStop/4102". This makes them unwieldy to copy/paste in Twitter, email, SMS, etc.

It'd be great if we could implement a simple URL shortener to make our URLs more shareable.

One simple idea is to create alternate routing that lets users use abbreviations. For instance, instead of this:

https://muni.opentransit.city/route/41/direction/41___I_F00/fromStop/6769/toStop/4102

users could share this:

https://muni.opentransit.city/r/41/d/I/f/6769/t/4102

or even

https://muni.opentransit.city/t/41/I/6769/4102

(the t/ at the start is to make sure no route number messes with our normal routing)

In other words, you want to losslessly compress the data encoded in the URL.

[hathix]

I considered base64 encoding the string, but it wouldn't make the text any shorter.

The fancy alternative is to create a database that maps randomly-generated shortcodes to full URLs. This is how bit.ly and other "real" URL shorteners do it. But that's a lot of work to build and maintain.

[hathix]

This is actually useful for things like #517, sharing links out