[search] Legacy search fallback support legacy query params (#99765)

* add support for deleted query param

* support tag query param in modes 2 and below

* handle dashboardIds

* hhandle dashboardUIDs

* handle folderUIDs query param

* handle page query param when hitting legacy storage

* handle sort query param

* handle type query param

* re-enable search fallback

* remove folder search workaround and fix /api/search to return both folders and dashboards when no title or type is provided

---------

Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

pkg/storage/unified/resource/search.go

@@ -10,6 +10,8 @@ import (
 	"sync"
 	"time"
 
+	dashboardv0alpha1 "github.com/grafana/grafana/pkg/apis/dashboard/v0alpha1"
+	folderv0alpha1 "github.com/grafana/grafana/pkg/apis/folder/v0alpha1"
 	"github.com/hashicorp/golang-lru/v2/expirable"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
@@ -651,3 +653,34 @@ func (s *builderCache) get(ctx context.Context, key NamespacedResource) (Documen
 	}
 	return s.defaultBuilder, nil
 }
+
+// AsResourceKey converts the given namespace and type to a search key
+func AsResourceKey(ns string, t string) (*ResourceKey, error) {
+	if ns == "" {
+		return nil, fmt.Errorf("missing namespace")
+	}
+	switch t {
+	case "folders", "folder":
+		return &ResourceKey{
+			Namespace: ns,
+			Group:     folderv0alpha1.GROUP,
+			Resource:  folderv0alpha1.RESOURCE,
+		}, nil
+	case "dashboards", "dashboard":
+		return &ResourceKey{
+			Namespace: ns,
+			Group:     dashboardv0alpha1.GROUP,
+			Resource:  dashboardv0alpha1.RESOURCE,
+		}, nil
+
+	// NOT really supported in the dashboard search UI, but useful for manual testing
+	case "playlist", "playlists":
+		return &ResourceKey{
+			Namespace: ns,
+			Group:     "playlist.grafana.app",
+			Resource:  "playlists",
+		}, nil
+	}
+
+	return nil, fmt.Errorf("unknown resource type")
+}