Document consumer README skeleton and add package Examples.

Co-authored-by: Cursor <cursoragent@cursor.com>

example_test.go

@@ -0,0 +1,89 @@
+package gonexapp_test
+
+import (
+	"encoding/base64"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+
+	gonexapp "gitea.neitzel.de/konrad/go-nc-exapp"
+)
+
+func ExampleUserFromRequest() {
+	token := base64.StdEncoding.EncodeToString([]byte("alice:secret"))
+	req := httptest.NewRequest(http.MethodGet, "/api", nil)
+	req.Header.Set("AUTHORIZATION-APP-API", token)
+
+	user, err := gonexapp.UserFromRequest(req)
+	if err != nil {
+		fmt.Println("err:", err)
+		return
+	}
+	fmt.Println(user)
+	// Output: alice
+}
+
+func ExampleCredentials_AuthHeaders() {
+	cred := gonexapp.Credentials{
+		BaseURL: "https://nextcloud.example", AppID: "myexapp", AppVersion: "0.1.0",
+		AAVersion: "1.0.0", AppSecret: "s", UserID: "alice",
+	}
+	h := cred.AuthHeaders()
+	fmt.Println(h.Get("EX-APP-ID"), h.Get("OCS-APIRequest") != "")
+	// Output: myexapp true
+}
+
+func ExampleNewAppAPIPreferences() {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.Contains(r.URL.Path, "get-values") {
+			_, _ = io.WriteString(w, `{"ocs":{"data":[{"configkey":"savedDefault","configvalue":"Zones"}]}}`)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		_, _ = io.WriteString(w, `{"ocs":{"data":{}}}`)
+	}))
+	defer srv.Close()
+
+	cred := gonexapp.Credentials{
+		BaseURL: srv.URL, AppID: "myexapp", AppVersion: "0.1.0", AAVersion: "1.0.0",
+		AppSecret: "s", UserID: "alice",
+	}
+	prefs := gonexapp.NewAppAPIPreferences(cred, "myexapp", "savedDefault")
+	prefs.Client = srv.Client()
+	prefs.OCS.Client = srv.Client()
+
+	value, err := prefs.Get()
+	if err != nil {
+		fmt.Println("err:", err)
+		return
+	}
+	if err := prefs.Set("Zones"); err != nil {
+		fmt.Println("set:", err)
+		return
+	}
+	fmt.Println(value)
+	// Output: Zones
+}
+
+func ExampleAccessGate_Wrap() {
+	inner := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = io.WriteString(w, "ok")
+	})
+	// Empty Required Groups: gate is inactive.
+	h := gonexapp.AccessGate{}.Wrap(inner)
+
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/api", nil))
+	fmt.Println(rec.Code, rec.Body.String())
+	// Output: 200 ok
+}
+
+func ExampleResolveRequiredGroups() {
+	fmt.Println(gonexapp.ResolveRequiredGroups("", false, nil))
+	fmt.Println(len(gonexapp.ResolveRequiredGroups("", true, []string{"ops"})))
+	// Output:
+	// []
+	// 0
+}