feat(configurations)!: flatten down, introduce meta.nix

Flatten down directory structure:
- From: `./hosts/${configuration-type}/${system}/{configuration,deploy}.nix`
-   To: `./hosts/${configuration-type}/{meta,configuration}.nix`
Keep `system` and `deploy-rs` config in `meta.nix`
Update `flake.lock`

hosts/nixos/__template__/deploy.nix

@@ -0,0 +1,42 @@
+{
+  # This is the hostname by which you'll refer to this machine using reploy-rs
+  hostname = "server";
+
+  # This is the user that deploy-rs will use when connecting.
+  # This will default to your own username if not specified anywhere
+  sshUser = "admin";
+
+  # This is the user that the profile will be deployed to (will use sudo if not the same as above).
+  # If `sshUser` is specified, this will be the default (though it will _not_ default to your own username)
+  user = "root";
+
+  # Which sudo command to use. Must accept at least two arguments:
+  # the user name to execute commands as and the rest is the command to execute
+  # This will default to "sudo -u" if not specified anywhere.
+  sudo = "doas -u";
+
+  # This is an optional list of arguments that will be passed to SSH.
+  sshOpts = [ "-p" "2121" ];
+
+  # Fast connection to the node. If this is true, copy the whole closure instead of letting the node substitute.
+  # This defaults to `false`
+  fastConnection = false;
+
+  # If the previous profile should be re-activated if activation fails.
+  # This defaults to `true`
+  autoRollback = true;
+
+  # See the earlier section about Magic Rollback for more information.
+  # This defaults to `true`
+  magicRollback = true;
+
+  # The path which deploy-rs will use for temporary files, this is currently only used by `magicRollback` to create an inotify watcher in for confirmations
+  # If not specified, this will default to `/tmp`
+  # (if `magicRollback` is in use, this _must_ be writable by `user`)
+  tempPath = "/home/someuser/.deploy-rs";
+
+  # Build the derivation on the target system. 
+  # Will also fetch all external dependencies from the target system's substituters.
+  # This default to `false`
+  remoteBuild = true;
+}