[full-ci] experimental search backport (#5221)

* experimental search backport
fix basic extractor resource name
move escapeQuery regex into global variable
minor pr review changes
rename DebounceDuration env variable
add document title and content when rebuilding bleve resource

Co-authored-by: David Christofas <dchristofas@owncloud.com>

services/search/pkg/content/extractor.go

@@ -0,0 +1,33 @@
+package content
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	provider "github.com/cs3org/go-cs3apis/cs3/storage/provider/v1beta1"
+)
+
+// Extractor is responsible to extract content and meta information from documents.
+//
+//go:generate mockery --name=Extractor
+type Extractor interface {
+	Extract(ctx context.Context, ri *provider.ResourceInfo) (Document, error)
+}
+
+func getFirstValue(m map[string][]string, key string) (string, error) {
+	if m == nil {
+		return "", errors.New("undefined map")
+	}
+
+	v, ok := m[key]
+	if !ok {
+		return "", fmt.Errorf("unknown key: %v", key)
+	}
+
+	if len(m) == 0 {
+		return "", fmt.Errorf("no values for: %v", key)
+	}
+
+	return v[0], nil
+}