add unit test for syncSecrets + new updateSecret func

docs/reference/cluster_manifest.md

@@ -129,7 +129,7 @@ These parameters are grouped directly under  the `spec` key in the manifest.
   password value will be replaced in the secrets which the operator reflects
   in the database, too. List only users here that rarely connect to the
   database, like a flyway user running a migration on Pod start. See more
-  details in the [administrator docs](https://github.com/zalando/postgres-operator/blob/master/docs/administrator.md#password-replacement-without-extra-roles).
+  details in the [administrator docs](https://github.com/zalando/postgres-operator/blob/master/docs/administrator.md#password-replacement-without-extra-users).
 
 * **databases**
   a map of database names to database owners for the databases that should be

docs/reference/operator_parameters.md

@@ -175,12 +175,12 @@ under the `users` key.
   `standby`.
 
 * **enable_password_rotation**
-  For all LOGIN roles that are not database owners the Operator can rotate
+  For all `LOGIN` roles that are not database owners the operator can rotate
   credentials in the corresponding K8s secrets by replacing the username and
   password. This means, new users will be added on each rotation inheriting
-  all priviliges from the original roles. The rotation date in the YYMMDD is
-  appended to the new user names. The timestamp of the next rotation is
-  written to the secret. The default is `false`.
+  all priviliges from the original roles. The rotation date (in YYMMDD format)
+  is appended to the names of the new user. The timestamp of the next rotation
+  is written to the secret. The default is `false`.
 
 * **password_rotation_interval**
   If password rotation is enabled (either from config or cluster manifest) the