checker: add standalone interactive form and test target

Implement RenderForm/ParseForm for the zonemasterProvider under the
standalone build tag, enabling browser-based interactive use. Also add
a `make test` target that builds with the same tag.

checker/interactive.go

@@ -0,0 +1,69 @@
+//go:build standalone
+
+package checker
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+func (p *zonemasterProvider) RenderForm() []sdk.CheckerOptionField {
+	return []sdk.CheckerOptionField{
+		{
+			Id:          "domainName",
+			Type:        "string",
+			Label:       "Domain name to check",
+			Placeholder: "example.com",
+			Required:    true,
+			Description: "Fully-qualified domain name to submit to the Zonemaster engine.",
+		},
+		{
+			Id:          "profile",
+			Type:        "string",
+			Label:       "Profile",
+			Placeholder: "default",
+			Description: "Zonemaster test profile to apply (engine-defined; usually \"default\").",
+		},
+		{
+			Id:          "language",
+			Type:        "string",
+			Label:       "Result language",
+			Placeholder: "en",
+			Description: "Language for human-readable test messages (en, fr, de, es, sv, da, fi, nb, nl, pt).",
+		},
+		{
+			Id:          "zonemasterAPIURL",
+			Type:        "string",
+			Label:       "Zonemaster API URL",
+			Placeholder: "https://zonemaster.net/api",
+			Description: "JSON-RPC endpoint of the Zonemaster backend to query.",
+		},
+	}
+}
+
+func (p *zonemasterProvider) ParseForm(r *http.Request) (sdk.CheckerOptions, error) {
+	domainName := strings.TrimSpace(r.FormValue("domainName"))
+	if domainName == "" {
+		return nil, errors.New("domainName is required")
+	}
+	domainName = strings.TrimSuffix(domainName, ".")
+
+	opts := sdk.CheckerOptions{
+		"domainName": domainName,
+	}
+
+	if v := strings.TrimSpace(r.FormValue("profile")); v != "" {
+		opts["profile"] = v
+	}
+	if v := strings.TrimSpace(r.FormValue("language")); v != "" {
+		opts["language"] = v
+	}
+	if v := strings.TrimSpace(r.FormValue("zonemasterAPIURL")); v != "" {
+		opts["zonemasterAPIURL"] = strings.TrimSuffix(v, "/")
+	}
+
+	return opts, nil
+}