Add a uci config file for matter and run matter as root

[fvb-mind]

• Add a matter uci config file with one config variable (wifi_iface)
• Matter could not access ubus --> running as root for now

Note: This PR also includes the change of #50 since we need it and it hasn't been merged yet

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[gemini-code-assist]

Code Review

This pull request adds rpcd as a dependency, installs a new UCI configuration file, and comments out the user and group parameters in the init script, causing the daemon to run as root. The review feedback highlights a security regression where the daemon runs as root instead of the unprivileged matter user; it is recommended to restore the unprivileged user and update the ACL permissions instead. Additionally, it is suggested to rename the matter_uci.defaults file to avoid confusion, as it is installed as a configuration file rather than a first-boot defaults script.

[gemini-code-assist]

Running the daemon as root instead of the unprivileged matter user is a significant security regression. The reason the daemon could not access ubus is likely because the matter user lacks the necessary permissions in service/matter-netman/files/matter_acl.json to access the uci ubus object (provided by rpcd, which was added as a dependency in this PR) or other required ubus objects.

Instead of running as root, we should keep the daemon running as the matter user and update service/matter-netman/files/matter_acl.json to grant the necessary ubus permissions. For example, to allow reading UCI configurations, you can add the uci object with the get method to the ACL file:

	"access": {
		"otbr": {
			"methods": ["*"]
		},
		"uci": {
			"methods": ["get"]
		}
	}

Suggested change

	#procd_set_param user matter
	#procd_set_param group matter
	procd_set_param user matter
	procd_set_param group matter

[ksperling-apple]

I think instead of running as root you should be able to just add the relevant objects to service/matter-netman/files/matter_acl.json to give the matter user access.

[gemini-code-assist]

The source file is named matter_uci.defaults, but it is installed directly as a UCI configuration file to /etc/config/matter. In OpenWrt, .defaults files typically refer to uci-defaults scripts (which are shell scripts executed on first boot). To avoid confusion, the source file should be renamed to matter.config or simply matter in the repository.

	$(INSTALL_DATA) ./files/matter.config $(1)/etc/config/matter

[ksperling-apple]

I think calling it matter.defaults is fine, have a look at otbr-agent.defaults for an example. They need to be installed into /etc/uci-defaults/; I think what you're doing here will overwrite the config file on a package upgrade.