Add passport settings

.env.example

@@ -195,6 +195,15 @@ AUTHENTICATION_GUARD=web
 AUTHENTICATION_GUARD_HEADER=REMOTE_USER
 AUTHENTICATION_GUARD_EMAIL=
 
+#
+# Firefly III generates a basic keypair for your OAuth tokens.
+# If you want, you can overrule the key with your own (secure) value.
+# It's also possible to set PASSPORT_PUBLIC_KEY_FILE or PASSPORT_PRIVATE_KEY_FILE
+# if you're using Docker secrets or similar solutions for secret management
+#
+PASSPORT_PRIVATE_KEY=
+PASSPORT_PUBLIC_KEY=
+
 #
 # Extra authentication settings
 #