Add support for groups in alpine-config

Only support creating empty groups for now

ref: https://cloudinit.readthedocs.io/en/latest/reference/modules.html#users-and-groups

lib/tiny-cloud/user-data/alpine-config

@@ -4,7 +4,7 @@
 
 INIT_ACTIONS_MAIN="$(insert_before create_default_user userdata_user $INIT_ACTIONS_MAIN)"
 INIT_ACTIONS_MAIN="$(insert_after set_hostname \
-	"userdata_bootcmd userdata_write_files userdata_ntp userdata_apk_cache userdata_apk_repositories userdata_package_update userdata_package_upgrade userdata_packages" \
+	"userdata_bootcmd userdata_groups userdata_write_files userdata_ntp userdata_apk_cache userdata_apk_repositories userdata_package_update userdata_package_upgrade userdata_packages" \
 	$INIT_ACTIONS_MAIN)"
 INIT_ACTIONS_MAIN="$(insert_after set_ssh_keys ssh_authorized_keys $INIT_ACTIONS_MAIN)"
 INIT_ACTIONS_FINAL="$INIT_ACTIONS_FINAL userdata_runcmd userdata_autoinstall"
@@ -233,6 +233,14 @@ init__userdata_runcmd() {
 	done
 }
 
+init__userdata_groups() {
+	local groups="$(get_userdata groups)"
+	for i in $groups; do
+		local group="$(get_userdata groups/$i)"
+		$MOCK addgroup $group
+	done
+}
+
 find_biggest_empty_disk() {
 	local d
 	for d in  "$ROOT"/sys/class/block/*/device; do

tests/tiny-cloud-alpine.test

@@ -16,6 +16,7 @@ init_tests \
 	userdata_user_missing_name \
 	userdata_create_default_user \
 	userdata_ssh_authorized_keys \
+	userdata_groups \
 	userdata_bootcmd \
 	userdata_write_files \
 	userdata_ntp \
@@ -178,6 +179,20 @@ userdata_bootcmd_body() {
 		tiny-cloud main
 }
 
+userdata_groups_body() {
+	fake_userdata_nocloud <<-EOF
+		#alpine-config
+		groups:
+		  - group1
+		  - group2
+	EOF
+	atf_check -e ignore -o ignore tiny-cloud early
+	atf_check \
+		-e match:"userdata_groups: done" \
+		-o match:"addgroup group1" -o match:"addgroup group2" \
+		tiny-cloud main
+}
+
 userdata_ntp_body() {
 	fake_userdata_nocloud <<-EOF
 		#alpine-config