Implement basic API scoping

internal/dis/component/auth/scopes/instances.go

@@ -0,0 +1,38 @@
+package scopes
+
+import (
+	"net/http"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
+	"github.com/FAU-CDI/wisski-distillery/internal/dis/component/auth"
+)
+
+type ListInstancesScope struct {
+	component.Base
+	Dependencies struct {
+		Auth *auth.Auth
+	}
+}
+
+var (
+	_ component.ScopeProvider = (*ListInstancesScope)(nil)
+)
+
+const (
+	ScopeInstanceDirectory Scope = "instances.directory"
+)
+
+func (*ListInstancesScope) Scope() component.ScopeInfo {
+	return component.ScopeInfo{
+		Scope:         ScopeInstanceDirectory,
+		Description:   "get a public directory of instances",
+		DeniedMessage: "",
+		TakesParam:    false,
+	}
+}
+
+func (lis *ListInstancesScope) HasScope(param string, r *http.Request) (bool, error) {
+	// TODO: at the moment everyone has this permission
+	// this should change in the future!
+	return true, nil
+}