Plugin docs or tutorials on hooks?

I have a custom field for users when they register. The user enters an ID, in this case the ID represents their job. Is there anyway to write a plugin that displays that custom field alongside the users screen name? Can we hack discourse to that extent? I don’t need a step by step just some light shines on a starting point. The end result would be a simple GET request to an API that returns the title associated with that ID…but for now I just want to get it displayed.

I would like the same thing - see my post here