Link to identifiers in Godoc for shared/client

[markylaing]

@kadinsayani noted that square brackets can be used to create links to identifiers in the Godoc: https://github.com/canonical/lxd/pull/15920#discussion_r2184603292_

I thought this happened automatically but the square brackets are required. It would be good to update at least the client and shared packages to do this to make the Godocs more useful.