chore(settings): refactor settings processing (#756)

- Better settings tree structure logged using `qdm12/gotree`
- Read settings from environment variables, then files, then secret files
- Settings methods to default them, merge them and override them
- `DNS_PLAINTEXT_ADDRESS` default changed to `127.0.0.1` to use DoT. Warning added if set to something else.
- `HTTPPROXY_LISTENING_ADDRESS` instead of `HTTPPROXY_PORT` (with retro-compatibility)

internal/configuration/settings/helpers/copy.go

@@ -0,0 +1,190 @@
+package helpers
+
+import (
+	"net"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+	"inet.af/netaddr"
+)
+
+func CopyStringPtr(original *string) (copied *string) {
+	if original == nil {
+		return nil
+	}
+	copied = new(string)
+	*copied = *original
+	return copied
+}
+
+func CopyBoolPtr(original *bool) (copied *bool) {
+	if original == nil {
+		return nil
+	}
+	copied = new(bool)
+	*copied = *original
+	return copied
+}
+
+func CopyUint8Ptr(original *uint8) (copied *uint8) {
+	if original == nil {
+		return nil
+	}
+	copied = new(uint8)
+	*copied = *original
+	return copied
+}
+
+func CopyUint16Ptr(original *uint16) (copied *uint16) {
+	if original == nil {
+		return nil
+	}
+	copied = new(uint16)
+	*copied = *original
+	return copied
+}
+
+func CopyIntPtr(original *int) (copied *int) {
+	if original == nil {
+		return nil
+	}
+	copied = new(int)
+	*copied = *original
+	return copied
+}
+
+func CopyDurationPtr(original *time.Duration) (copied *time.Duration) {
+	if original == nil {
+		return nil
+	}
+	copied = new(time.Duration)
+	*copied = *original
+	return copied
+}
+
+func CopyLogLevelPtr(original *logging.Level) (copied *logging.Level) {
+	if original == nil {
+		return nil
+	}
+	copied = new(logging.Level)
+	*copied = *original
+	return copied
+}
+
+func CopyIP(original net.IP) (copied net.IP) {
+	if original == nil {
+		return nil
+	}
+	copied = make(net.IP, len(original))
+	copy(copied, original)
+	return copied
+}
+
+func CopyIPNet(original net.IPNet) (copied net.IPNet) {
+	if original.IP != nil {
+		copied.IP = make(net.IP, len(original.IP))
+		copy(copied.IP, original.IP)
+	}
+
+	if original.Mask != nil {
+		copied.Mask = make(net.IPMask, len(original.Mask))
+		copy(copied.Mask, original.Mask)
+	}
+
+	return copied
+}
+
+func CopyIPNetPtr(original *net.IPNet) (copied *net.IPNet) {
+	if original == nil {
+		return nil
+	}
+
+	copied = new(net.IPNet)
+	*copied = CopyIPNet(*original)
+	return copied
+}
+
+func CopyNetaddrIP(original netaddr.IP) (copied netaddr.IP) {
+	b, err := original.MarshalBinary()
+	if err != nil {
+		panic(err)
+	}
+
+	err = copied.UnmarshalBinary(b)
+	if err != nil {
+		panic(err)
+	}
+
+	return copied
+}
+
+func CopyIPPrefix(original netaddr.IPPrefix) (copied netaddr.IPPrefix) {
+	b, err := original.MarshalText()
+	if err != nil {
+		panic(err)
+	}
+
+	err = copied.UnmarshalText(b)
+	if err != nil {
+		panic(err)
+	}
+
+	return copied
+}
+
+func CopyStringSlice(original []string) (copied []string) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]string, len(original))
+	copy(copied, original)
+	return copied
+}
+
+func CopyUint16Slice(original []uint16) (copied []uint16) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]uint16, len(original))
+	copy(copied, original)
+	return copied
+}
+
+func CopyIPNetSlice(original []net.IPNet) (copied []net.IPNet) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]net.IPNet, len(original))
+	for i := range original {
+		copied[i] = CopyIPNet(original[i])
+	}
+	return copied
+}
+
+func CopyIPPrefixSlice(original []netaddr.IPPrefix) (copied []netaddr.IPPrefix) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]netaddr.IPPrefix, len(original))
+	for i := range original {
+		copied[i] = CopyIPPrefix(original[i])
+	}
+	return copied
+}
+
+func CopyNetaddrIPsSlice(original []netaddr.IP) (copied []netaddr.IP) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]netaddr.IP, len(original))
+	for i := range original {
+		copied[i] = CopyNetaddrIP(original[i])
+	}
+
+	return copied
+}