Fulltext implementation incl. config (#2480)

This adds the main component of the fulltext search.
This PR doesn't do anything yet, besides creating an empty fulltextindex
folder if enabled. Indexing events is done in a separate PR.

internal/fulltext/bleve_wasm.go

@@ -0,0 +1,65 @@
+// Copyright 2022 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fulltext
+
+import (
+	"github.com/matrix-org/dendrite/setup/config"
+	"time"
+)
+
+type Search struct{}
+type IndexElement struct {
+	EventID        string
+	RoomID         string
+	Content        string
+	ContentType    string
+	StreamPosition int64
+}
+
+type SearchResult struct {
+	Status   interface{}   `json:"status"`
+	Request  *interface{}  `json:"request"`
+	Hits     []interface{} `json:"hits"`
+	Total    uint64        `json:"total_hits"`
+	MaxScore float64       `json:"max_score"`
+	Took     time.Duration `json:"took"`
+	Facets   interface{}   `json:"facets"`
+}
+
+func (i *IndexElement) SetContentType(v string) {}
+
+func New(cfg config.Fulltext) (fts *Search, err error) {
+	return &Search{}, nil
+}
+
+func (f *Search) Close() error {
+	return nil
+}
+
+func (f *Search) Index(e IndexElement) error {
+	return nil
+}
+
+func (f *Search) BatchIndex(elements []IndexElement) error {
+	return nil
+}
+
+func (f *Search) Delete(eventID string) error {
+	return nil
+}
+
+func (f *Search) Search(term string, roomIDs, keys []string, limit, from int, orderByStreamPos bool) (SearchResult, error) {
+	return SearchResult{}, nil
+}