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.

Makefile

@@ -6,12 +6,12 @@ CHECKER_SOURCES := main.go $(wildcard checker/*.go)
 
 GO_LDFLAGS := -X main.Version=$(CHECKER_VERSION)
 
-.PHONY: all plugin docker clean
+.PHONY: all plugin docker test clean
 
 all: $(CHECKER_NAME)
 
 $(CHECKER_NAME): $(CHECKER_SOURCES)
-	go build -ldflags "$(GO_LDFLAGS)" -o $@ .
+	go build -tags standalone -ldflags "$(GO_LDFLAGS)" -o $@ .
 
 plugin: $(CHECKER_NAME).so
 
@@ -21,5 +21,8 @@ $(CHECKER_NAME).so: $(CHECKER_SOURCES) $(wildcard plugin/*.go)
 docker:
 	docker build --build-arg CHECKER_VERSION=$(CHECKER_VERSION) -t $(CHECKER_IMAGE) .
 
+test:
+	go test -tags standalone ./...
+
 clean:
 	rm -f $(CHECKER_NAME) $(CHECKER_NAME).so

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
+}