api: node status: document boot-info and current-kernel in return schema

I recently added the same info to PMG and added them to the return
schema, so copying them over here comes for free, and while far from
complete but better than nothing.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

PVE/API2/Nodes.pm

@@ -396,8 +396,47 @@ __PACKAGE__->register_method({
     },
     returns => {
 	type => "object",
+	additionalProperties => 1,
 	properties => {
-
+	    # TODO: document remaing ones
+	    'boot-info' => {
+		description => "Meta-information about the boot mode.",
+		type => 'object',
+		properties => {
+		    mode => {
+			description => 'Through which firmware the system got booted.',
+			type => 'string',
+			enum => [qw(efi legacy-bios)],
+		    },
+		    secureboot => {
+			description => 'System is booted in secure mode, only applicable for the "efi" mode.',
+			type => 'boolean',
+			optional => 1,
+		    },
+		},
+	    },
+	    'current-kernel' => {
+		description => "The uptime of the system in seconds.",
+		type => 'object',
+		properties => {
+		    sysname => {
+			description => 'OS kernel name (e.g., "Linux")',
+			type => 'string',
+		    },
+		    release => {
+			description => 'OS kernel release (e.g., "6.8.0")',
+			type => 'string',
+		    },
+		    version => {
+			description => 'OS kernel version with build info',
+			type => 'string',
+		    },
+		    machine => {
+			description => 'Hardware (architecture) type',
+			type => 'string',
+		    },
+		},
+	    },
 	},
     },
     code => sub {