How to store user metadata from external system in Atlassian?

[Tommy Augustine]

We're trying to find a common field between Jira and another external CRM. Naturally, I'd think to use an email address, but then Atlassian changed the ability to get the email address of the user. So, now we're looking at storing the Work Day ID somewhere in Jira and using that as a foreign key. My question is, where can we programmatically store that working day meta data in Jira for each user?  Is there another alternative solution to this? 

[Mikael Sandberg]

You could store that in the user properties, and access it via automation and smart values, similar to this article describing how to store the user's Slack ID as a property in Jira so you can DM them via automation.