Update migration guide, move documentation od dbus_native to cgroups

Signed-off-by: Yashodhan Joshi <[email protected]>

MirgationGuide.md

@@ -2,7 +2,12 @@
 
 This contains information for migrating library versions.
 
-## V0.1.0 -> v0.2.0
+## v0.2.0 -> v0.3.0
+
+### libcgroups
+- Switched from dbus-rs to a native dbus implementation see [#2208](https://github.com/containers/youki/issues/2208) for motivation behind this. This replaces the `dbus` module with `dbus_native` module. However, As this is not in public interface for the crate, the users of this crate should not need any code changes. As this removes the dependency on the `libdbus` system library, you can uninstall it if desired.
+
+## v0.1.0 -> v0.2.0
 
 ### libcontainer
 

crates/libcgroups/src/systemd/mod.rs

@@ -4,7 +4,7 @@ mod controller;
 pub mod controller_type;
 mod cpu;
 mod cpuset;
-pub mod dbus_native;
+mod dbus_native;
 pub mod manager;
 mod memory;
 mod pids;

docs/src/developer/libcgroups.md

@@ -28,3 +28,14 @@ This crates exposes several functions and modules that can be used to work with
 - Cgroups V2 module which deal with implementing a cgroup manager for systems which have cgroups v2
 
 As youki currently depends on systemd as an init system, this crate also exposes module systemd, which provides interface for working with systemd related operations. [systemd resource control](https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html) is a good place to read more about systemd and its involvement in resource control.
+
+## Dbus Native
+
+This module is the native implementation of dbus connection functionality used for connecting with systemd via dbus. Refer to [this issue discussion](https://github.com/containers/youki/issues/2208) following for the discussion regarding moving away from existing dbus-interfacing library.
+
+Note that this implements the minimal required functionality for youki to use dbus, and thus does not have all the dbus features.
+
+- Refer to see [dbus specification](https://dbus.freedesktop.org/doc/dbus-specification.html) and [header format](https://dbus.freedesktop.org/doc/api/html/structDBusHeader.html) for the individual specifications.
+
+- For systemd interface and types, you can generate the following file and take help from the auto-generated functions
+`dbus-codegen-rust -s -g -m None -d org.freedesktop.systemd1 -p /org/freedesktop/systemd1`, see https://github.com/diwic/dbus-rs