config-sso.txt: Update sections that talk about external IDs

The account_external_ids table doesn't exist anymore. External IDs are
now stored in NoteDb.

Change-Id: I2304bfca78dbda59d47e1fb4bd0acf5006ac26bd
Signed-off-by: Edwin Kempin <ekempin@google.com>
diff --git a/Documentation/config-sso.txt b/Documentation/config-sso.txt
index 04949bf..bdd52f7 100644
--- a/Documentation/config-sso.txt
+++ b/Documentation/config-sso.txt
@@ -50,8 +50,8 @@
 
 === Database Schema
 
-User identities obtained from OpenID providers are stored into the
-`account_external_ids` table.
+User identities obtained from OpenID providers are stored as
+link:config-accounts.html#external-ids[external IDs].
 
 === Multiple Identities
 
@@ -135,11 +135,10 @@
 
 === Database Schema
 
-User identities are stored in the `account_external_ids` table.
-The user string obtained from the authorization header has the prefix
-"gerrit:" and is stored in the `external_id` field.  For example,
-if a username was "foo" then the external_id field would be populated
-with "gerrit:foo".
+User identities are stored as
+link:config-accounts.html#external-ids[external IDs] with "gerrit" as
+scheme. The user string obtained from the authorization header is
+stored as ID of the external ID.
 
 
 == Computer Associates Siteminder
@@ -193,11 +192,10 @@
 
 === Database Schema
 
-User identities are stored in the `account_external_ids` table.
-The user string obtained from Siteminder (e.g. the value in the
-"SM_USER" HTTP header) has the prefix "gerrit:" and is stored in the
-`external_id` field.  For example, if a Siteminder username was "foo"
-then the external_id field would be populated with "gerrit:foo".
+User identities are stored as
+link:config-accounts.html#external-ids[external IDs] with "gerrit" as
+scheme. The user string obtained from Siteminder (e.g. the value in the
+"SM_USER" HTTP header) is stored as ID in the external ID.
 
 GERRIT
 ------