docs: add instructions for migrating from old versions, remove obsolite docs, add openssl example to windows guide

docs/INSTALL_WINDOWS.md

@@ -59,7 +59,7 @@ GRANT Alter,Create,Delete,Drop,Index,Insert,References,Select,Update ON aime.* T
     - Put the password you created for the aime user into the `database` section.
     - Put in the aimedb key (YOU DO NOT GENERATE THIS KEY, FIND IT SOMEWHERE).
     - Set your hostname to be whatever hostname or IP address games can reach your server at (many games reject localhost and 127.0.0.1).
-    - Optional: generate base64-encoded secrets for aimedb and frontend.
+    - Optional: generate base64-encoded secrets for aimedb and frontend using something like `openssl rand -base64 64`. It is advised to make all secrets different.
     - See [config.md](docs/config.md) for a full list of options.
 - edit `idz.yaml`
     - If you don't plan on anyone using your server to play Initial D Zero, it is best to disable it to cut down on console spam on boot.