[folks] Clarify immutability of Persona.uid

[Philip Withnall <pwithnall src gnome org>]

commit c40b69f3b3c3dfb5890b964f2ec1e9daacc5a0aa
Author: Philip Withnall <philip tecnocode co uk>
Date:   Sun Nov 21 14:15:36 2010 +0000

    Clarify immutability of Persona.uid

 folks/persona.vala |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/folks/persona.vala b/folks/persona.vala
index f8a3fa5..8f36b81 100644
--- a/folks/persona.vala
+++ b/folks/persona.vala
@@ -52,6 +52,11 @@ public abstract class Folks.Persona : Object
    * This is the canonical way to refer to any Persona. It is guaranteed to be
    * unique within the Persona's { link PersonaStore}.
    *
+   * A Persona's UID is immutable over the life of the Persona in the backing
+   * store, so a given UID is guaranteed to refer to the same Persona each time
+   * libfolks is used, until the Persona is permanently removed from its backing
+   * store.
+   *
    * @see Persona.build_uid
    * @see Persona.split_uid
    */