docs: Move developer guides into the Developer section

nix fmt

address davhau review

docs/site/developer/extensions/templates/disk/disko-templates.md

@@ -0,0 +1,94 @@
+
+!!! Danger ":fontawesome-solid-road-barrier: Under Construction :fontawesome-solid-road-barrier:"
+    Currently under construction use with caution
+
+    :fontawesome-solid-road-barrier: :fontawesome-solid-road-barrier: :fontawesome-solid-road-barrier:
+
+
+## Structure
+
+A disk template consists of exactly two files
+
+- `default.nix`
+- `README.md`
+
+```sh
+└── single-disk
+    ├── default.nix
+    └── README.md
+```
+
+## `default.nix`
+
+Placeholders are filled with their machine specific options when a template is used for a machine.
+
+The user can choose any valid options from the hardware report.
+
+The file itself is then copied to `machines/{machineName}/disko.nix` and will be automatically loaded by the machine.
+
+`single-disk/default.nix`
+```
+{
+  disko.devices = {
+    disk = {
+      main = {
+        device = "{{mainDisk}}";
+        ...
+      };
+    };
+  };
+}
+```
+
+## Placeholders
+
+Each template must declare the options of its placeholders depending on the hardware-report.
+
+`api/disk.py`
+```py
+templates: dict[str, dict[str, Callable[[dict[str, Any]], Placeholder]]] = {
+    "single-disk": {
+        # Placeholders
+        "mainDisk": lambda hw_report: Placeholder(
+            label="Main disk", options=hw_main_disk_options(hw_report), required=True
+        ),
+    }
+}
+```
+
+Introducing new local or global placeholders requires contributing to clan-core `api/disks.py`.
+
+### Predefined placeholders
+
+Some placeholders provide predefined functionality
+
+- `uuid`: In most cases we recommend adding a unique id to all disks. This prevents the system to false boot from i.e. hot-plugged devices.
+    ```
+    disko.devices = {
+      disk = {
+        main = {
+          name = "main-{{uuid}}";
+          ...
+        }
+      }
+    }
+    ```
+
+
+## Readme
+
+The readme frontmatter must be of the same format as modules frontmatter.
+
+```markdown
+---
+description = "Simple disk schema for single disk setups"
+---
+
+# Single disk
+
+Use this schema for simple setups where ....
+
+```
+
+
+The format and fields of this file is not clear yet. We might change that once fully implemented.