Feature/Bugfix: IPv6 blocking (#428)

- Feature/Bugfix: Block all IPv6 traffic with `ip6tables` by default
- Feature: Adapt existing firewall code to handle IPv4 and IPv6, depending on user inputs and environment
- Maintenance: improve error wrapping in the firewall package

internal/firewall/iptablesmix.go

@@ -0,0 +1,21 @@
+package firewall
+
+import (
+	"context"
+)
+
+func (c *configurator) runMixedIptablesInstructions(ctx context.Context, instructions []string) error {
+	for _, instruction := range instructions {
+		if err := c.runMixedIptablesInstruction(ctx, instruction); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *configurator) runMixedIptablesInstruction(ctx context.Context, instruction string) error {
+	if err := c.runIptablesInstruction(ctx, instruction); err != nil {
+		return err
+	}
+	return c.runIP6tablesInstruction(ctx, instruction)
+}