Add userID or systemID field to the Contact object

[dss70]

Is it possible to add userID or systemID field to the Contact object? Users usually identified by a unique id of an external system.

[jeremystretch]

It would probably be best to use a custom field for this, as we can't assume what such an ID might look like (its data type, format, etc.).

[dss70]

In my opinion this would be a simple text field which could contain any kind of alphanumeric ID.