Private
This class converts instances supplied to intern to a common instance within the JVM, amongst all those instances that have been submitted. It uses weak references to avoid memory leaks.
NOTE: the Guava interners are Beta, so upgrading Guava may result in us having to adapt this code.
System properties allow disabling, in the event an issue is uncovered in a live environment. The correct default for the concurrency setting is the result of performance evaluation.