Generate and serve sourcemaps for javascript

[thatbudakguy]

javascript errors reported to honeybadger are difficult to diagnose because the trace points into the minified version of the file, see e.g. #2654. some of these errors occur constantly and have gone unaddressed for a long time.

given that sprockets v4 supports sourcemaps and DHH expressed support for shipping them to production, not just development, it seems reasonable practice to generate and serve sourcemaps so that we can more accurately debug issues with minified/compiled assets in prod.

it's unclear if sprockets actually supports generating the sourcemaps in a helpful way. we might want to instead change the JS compressor to terser (which is more actively developed) and can generate sourcemaps on its own.

[thatbudakguy]

@cbeer do you have thoughts/opinions on this? is this something we've tried on other apps?

[cbeer]

👍 .

[thatbudakguy]

waiting to try out a new approach on NTA, since it's a greenfield app. this solution and others using Uglifier don't seem to preserve file hierarchy in the sourcemap, which I think is important, and they also don't append the sourceMappingUrl= comment without some hacking, which is annoying.

[corylown]

We should look at this when we're working on SearchWorks maintenance.