Hi @SueRocha, thank you for reporting this issue.
Our apologies, the publish of ACSB version 5.1.0 was incomplete and not all packages were published initially. This has now been resolved and all packages are now available at version 5.1.0.
You can now use ForgeContextRetriever to retrieve the Forge Invocation Token from within your ACSB app. We have also shared a sample app detailing how to use it to make authenticated API calls back to Forge Storage.
As @markrekveld mentions, there is currently no long term token provided by Forge. The Forge Invocation Token is provided as part of a request from Forge to your remote backend, and is only intended to be used within the context of that request.
As such, to be able to use this token, you do need to be responding to a Forge request such as a web trigger, product event trigger, or specific usage of the invokeRemote function from a frontend UI or backend Forge function context.
We are currently working on an improvement to allow you to store the authentication tokens provided in the Forge Invocation Token, and use them outside of the context of a specific request. For more details, please see RFC-8 Forge Remote - Milestone 3: Remote access to product APIs at any time.