fix: setting firewall rules not working correctly

Because the Firewall API expects a different JSON formatting than it responds with (some fields must be omitted even though they are included in the response) we have to create an intermediate struct to marshal rules properly.

See hetznercloud/cli#725

hcloud/firewall.go

@@ -298,7 +298,35 @@ type FirewallSetRulesOpts struct {
 
 // SetRules sets the rules of a Firewall.
 func (c *FirewallClient) SetRules(ctx context.Context, firewall *Firewall, opts FirewallSetRulesOpts) ([]*Action, *Response, error) {
-	reqBody := firewallSetRulesOptsToSchema(opts)
+	s := firewallSetRulesOptsToSchema(opts)
+
+	// We can't use the FirewallRule struct here, because unlike in the response some fields must be omitted when empty.
+	type firewallRule struct {
+		Direction      string   `json:"direction"`
+		SourceIPs      []string `json:"source_ips,omitempty"`
+		DestinationIPs []string `json:"destination_ips,omitempty"`
+		Protocol       string   `json:"protocol"`
+		Port           *string  `json:"port,omitempty"`
+		Description    *string  `json:"description,omitempty"`
+	}
+
+	rules := make([]firewallRule, 0, len(s.Rules))
+	for _, r := range s.Rules {
+		rules = append(rules, firewallRule{
+			Direction:      r.Direction,
+			SourceIPs:      r.SourceIPs,
+			DestinationIPs: r.DestinationIPs,
+			Protocol:       r.Protocol,
+			Port:           r.Port,
+			Description:    r.Description,
+		})
+	}
+	reqBody := struct {
+		Rules []firewallRule `json:"rules"`
+	}{
+		Rules: rules,
+	}
+
 	reqBodyData, err := json.Marshal(reqBody)
 	if err != nil {
 		return nil, nil, err