Use internal URL shortener for URL on the share page

[azvoleff]

Not an immediate need, but on the "share" tool, the URL should be shortened to be more email friendly. To do this well without running into issues with external shorteners being blocked, I'd suggest we add an API endpoint, so that urls like:

https://foodsecurityiap.resilienceatlas.org/map?tab=layers&center=lat%3D-0.7470491450051796%26lng%3D15.402832031250002&layers=%5B%7B%22id%22%3A1458%2C%22opacity%22%3A1%2C%22order%22%3A0%7D%2C%7B%22id%22%3A1463%2C%22opacity%22%3A1%2C%22order%22%3A1%7D%5D&zoom=5#

could instead be something like:

https://foodsecurityiap.resilienceatlas.org/share/2sk4c8

This could be implemented by adding a table of share links, so that the id passed to the share endpoint could automatically pull up the correct long version of the link noted above