refactor: docgen and config examples

Short version is: move from global variables/`init()` function into
explicit functions.

`docgen` was updated to skip creating any top-level global variables,
now `Doc` information is generated on the fly when it is accessed.
Talos itself doesn't marshal the configuration often, so in general it
should never be accessed for Talos (but will be accessed e.g. for
`talosctl`).

Machine config examples were changed manually from variables to
functions returning a value and moved to a separate file.

There are no changes to the output of `talosctl gen config`.

There is a small change to the generated documentation, which I believe
is a correct one, as previously due to value reuse it was clobbered with
other data.

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

internal/pkg/tui/installer/state.go

@@ -17,6 +17,7 @@ import (
 	"github.com/siderolabs/talos/internal/pkg/tui/components"
 	"github.com/siderolabs/talos/pkg/images"
 	machineapi "github.com/siderolabs/talos/pkg/machinery/api/machine"
+	"github.com/siderolabs/talos/pkg/machinery/config/encoder"
 	"github.com/siderolabs/talos/pkg/machinery/config/machine"
 	"github.com/siderolabs/talos/pkg/machinery/config/types/v1alpha1"
 	"github.com/siderolabs/talos/pkg/machinery/constants"
@@ -103,12 +104,12 @@ func NewState(ctx context.Context, installer *Installer, conn *Connection) (*Sta
 	networkConfigItems := []*components.Item{
 		components.NewItem(
 			"Hostname",
-			v1alpha1.NetworkConfigDoc.Describe("hostname", true),
+			describe[v1alpha1.NetworkConfig]("hostname", true),
 			&opts.MachineConfig.NetworkConfig.Hostname,
 		),
 		components.NewItem(
 			"DNS Domain",
-			v1alpha1.ClusterNetworkConfigDoc.Describe("dnsDomain", true),
+			describe[v1alpha1.ClusterNetworkConfig]("dnsDomain", true),
 			&opts.ClusterConfig.ClusterNetwork.DnsDomain,
 		),
 	}
@@ -148,10 +149,10 @@ func NewState(ctx context.Context, installer *Installer, conn *Connection) (*Sta
 
 	if !conn.ExpandingCluster() {
 		networkConfigItems = append(networkConfigItems,
-			components.NewSeparator(v1alpha1.ClusterNetworkConfigDoc.Describe("cni", true)),
+			components.NewSeparator(describe[v1alpha1.ClusterNetworkConfig]("cni", true)),
 			components.NewItem(
 				"Type",
-				v1alpha1.ClusterNetworkConfigDoc.Describe("cni", true),
+				describe[v1alpha1.ClusterNetworkConfig]("cni", true),
 				&state.cni,
 				components.NewTableHeaders("CNI", "description"),
 				constants.FlannelCNI, "CNI used by Talos by default",
@@ -164,11 +165,11 @@ func NewState(ctx context.Context, installer *Installer, conn *Connection) (*Sta
 		NewPage("Installer Params",
 			components.NewItem(
 				"Image",
-				v1alpha1.InstallConfigDoc.Describe("image", true),
+				describe[v1alpha1.InstallConfig]("image", true),
 				&opts.MachineConfig.InstallConfig.InstallImage,
 			),
 			components.NewSeparator(
-				v1alpha1.InstallConfigDoc.Describe("disk", true),
+				describe[v1alpha1.InstallConfig]("disk", true),
 			),
 			components.NewItem(
 				"Install Disk",
@@ -180,18 +181,18 @@ func NewState(ctx context.Context, installer *Installer, conn *Connection) (*Sta
 		NewPage("Machine Config",
 			components.NewItem(
 				"Machine Type",
-				v1alpha1.MachineConfigDoc.Describe("type", true),
+				describe[v1alpha1.MachineConfig]("type", true),
 				&opts.MachineConfig.Type,
 				machineTypes...,
 			),
 			components.NewItem(
 				"Cluster Name",
-				v1alpha1.ClusterConfigDoc.Describe("clusterName", true),
+				describe[v1alpha1.ClusterConfig]("clusterName", true),
 				&opts.ClusterConfig.Name,
 			),
 			components.NewItem(
 				"Control Plane Endpoint",
-				v1alpha1.ControlPlaneConfigDoc.Describe("endpoint", true),
+				describe[v1alpha1.ControlPlaneConfig]("endpoint", true),
 				&opts.ClusterConfig.ControlPlane.Endpoint,
 			),
 			components.NewItem(
@@ -201,7 +202,7 @@ func NewState(ctx context.Context, installer *Installer, conn *Connection) (*Sta
 			),
 			components.NewItem(
 				"Allow Scheduling on Control Planes",
-				v1alpha1.ClusterConfigDoc.Describe("allowSchedulingOnControlPlanes", true),
+				describe[v1alpha1.ClusterConfig]("allowSchedulingOnControlPlanes", true),
 				&opts.ClusterConfig.AllowSchedulingOnControlPlanes,
 			),
 		),
@@ -268,27 +269,27 @@ func configureAdapter(installer *Installer, opts *machineapi.GenerateConfigurati
 				items := []*components.Item{
 					components.NewItem(
 						"Use DHCP",
-						v1alpha1.DeviceDoc.Describe("dhcp", true),
+						describe[v1alpha1.Device]("dhcp", true),
 						&adapterSettings.Dhcp,
 					),
 					components.NewItem(
 						"Ignore",
-						v1alpha1.DeviceDoc.Describe("ignore", true),
+						describe[v1alpha1.Device]("ignore", true),
 						&adapterSettings.Ignore,
 					),
 					components.NewItem(
 						"CIDR",
-						v1alpha1.DeviceDoc.Describe("cidr", true),
+						describe[v1alpha1.Device]("cidr", true),
 						&adapterSettings.Cidr,
 					),
 					components.NewItem(
 						"MTU",
-						v1alpha1.DeviceDoc.Describe("mtu", true),
+						describe[v1alpha1.Device]("mtu", true),
 						&adapterSettings.Mtu,
 					),
 					components.NewItem(
 						"Route Metric",
-						v1alpha1.DeviceDoc.Describe("dhcpOptions", true),
+						describe[v1alpha1.Device]("dhcpOptions", true),
 						&adapterSettings.DhcpOptions.RouteMetric,
 					),
 				}
@@ -339,3 +340,13 @@ func configureAdapter(installer *Installer, opts *machineapi.GenerateConfigurati
 			})
 	}
 }
+
+type documentable interface {
+	Doc() *encoder.Doc
+}
+
+func describe[T documentable](field string, short bool) string {
+	var zeroT T
+
+	return zeroT.Doc().Describe(field, short)
+}