Add comment describing -Dwdt.config.model.encryption.secret option

Author: rakillen

installer/src/main/lib/tool.properties

@@ -78,3 +78,21 @@ store.discovered.passwords.in.clear.text=false
 # ones passed on the command-line.
 #
 store.discover.admin_credentials=true
+
+#
+# the property model.encryption.secret specifies the name of
+# a secret containing a passphrase to decrypt the model.
+# this property can't be specified as part of tool.properties,
+# but should be specified on the Java command line as
+# -Dwdt.config.model.encryption.secret=<secretname>
+#
+# the secret should be located in one of the directories specified
+# in the WDT_MODEL_SECRETS_DIRS environment variable,
+# and should contain the key "passphrase"
+#
+# the WDT_MODEL_SECRETS variable is described in WDT documentation
+# under Concepts / Metadata Model
+#
+# WKO currently sets WDT_MODEL_SECRETS variable and uses it
+# to resolve secret tokens in the model
+#