The REST adapter generates paths with the /tags/ prefix indescriminately,
but individual tag paths have been moved under the /tag/ prefix to allow
tags with names that would otherwise cause ambiguity like c.
* DEV: Move `Discourse.getURL` and related functions to a module
* DEV: Remove `Discourse.getURL` and `Discourse.getURLWithCDN`
* FIX: `get-url` is required for server side code
* DEV: Deprecate `BaseUri` too.