RFE: Allow retrieving plugin version in runtime

[bkabrda]

Hey folks!
I have an RFE that I'd love to see implemented - allowing retrieving the plugin version in runtime. Here's my usecase:

I'm working on the Datadog CF resources [1] and we've started some work to modify the User-Agent header (used in calls to the Datadog API) to include more useful information. We'd like to be able to add the Java plugin version to the header, so that we could easily make stats about how users are migrating to newer builds (obviously we could just include the version of the resource and infer plugin version from that, but then we'd have to maintain a mapping of all our resources versions to plugin versions, which would be an unnecessary burden).

I'm not a great Java packaging expert, but I guess there are generally two ways to do this: a generated class in the plugin with a static getPluginVersion method that we would call or a .properties file that we could load and read as a resource. Both would work for us.

If, by any chance, this is already possible and I just didn't find the way to do it, please let me know :)

Thanks for considering!

[1] https://github.com/DataDog/datadog-cloudformation-resources/