Use substr() instead of array index syntax to access the first
character of the endpoint host string, as ucode does not support
array-style indexing on strings.
Fixes: https://github.com/openwrt/openwrt/issues/22116
Fixes: 8f977b4a40 ("wireguard-tools: fix handling of multi-value config options")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Config options like addresses and ip6prefix can be passed as either a
space-separated string or an array. Add a to_array() helper and use it
consistently for all multi-value options (addresses, ip6prefix,
allowed_ips).
Fixes: https://github.com/openwrt/openwrt/issues/22102
Fixes: 41bc454602 ("wireguard-tools: rewrite proto handler in ucode")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
