Changes to make it possible to extend the functionality of the registry.

[jcohen]

Overview

I have the need to limit the cardinality of metrics published to NR, but I'd like to still track metrics with unlimited cardinality and only limit the metrics sent to the top-N when they are published. In order to accomplish this, this PR introduces changes to the registry and its builder to make it more amenable to extension.

Details

• Changed the visibility of certain methods (e.g. the constructor) and added extensibility hooks to NewRelicRegistry#publish and NewRelictRegistryBuilder#build
• Added a new interface to the builder that allows its existing functionality to be reused, but still allow for creating a registry of any type (so long as it extends NewRelicRegistry).

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[kford-newrelic]

@jcohen thank you for this PR submission! We've added this to our backlog and will consider it for a future release. However please keep in mind that we have quite a bit of work on our agent roadmap, so it may take us a while to action this. Thanks again!

[kford-newrelic]

@jcohen thank you for the PR but since we've chosen to close this repo, no further enhancements will be made.