URI::Generic#set_userinfo

(::String? user, ?::String? password) -> [ ::String?, ::String? ]

set_userinfo(user, password = nil)

# File tmp/rubies/ruby-3.4.1/lib/uri/generic.rb, line 509
def set_userinfo(user, password = nil)
  unless password
    user, password = split_userinfo(user)
  end
  @user     = user
  @password = password if password

  [@user, @password]
end

Protected setter for the user component, and password if available (with validation).