docs: add basic garage CLI usage

docs/garage.md

@@ -0,0 +1,45 @@
+# Garage
+
+### CLI usage
+
+Required:
+
+- garage RPC credentials
+- [SSH access to host `trinkgenossin`](./administrative-access.md#ssh-access)
+
+First, find the rpc secret in the shared keepass, searching for 'garage rpc secret'.
+Then connect to `trinkgenossin` via SSH and export the secret with a initial few spaces
+in the command to avoid adding it to the shell history:
+
+```
+    export GARAGE_RPC_SECRET=<long-secret>
+```
+
+Now, you can run the following command to check the cluster status:
+
+```
+garage status
+```
+
+
+Command to list all existing buckets:
+
+```
+garage bucket list
+```
+
+
+The following commands can be used to create a new bucket and access key:
+
+```
+garage bucket create mastodon
+
+garage key create mastodon-key
+
+garage bucket allow mastodon --read --write --key mastodon-key
+```
+
+Further reading:
+- https://garagehq.deuxfleurs.fr/documentation/quick-start/
+- https://garagehq.deuxfleurs.fr/documentation/connect/
+- https://garagehq.deuxfleurs.fr/documentation/connect/apps/#mastodon