Get a user by email or identifier.
See also
Other users functions:
amber.group(),
amber.groups(),
amber.users()
Examples
if (FALSE) { # \dontrun{
a <- amber.login("https://amber-demo.obiba.org")
amber.user(a, id = "jim@muse.com")
amber.user(a, id = "6151b512268f582926d37f90")
amber.logout(a)
} # }