Preparations for removing BaseDendrite (#3016)

Preparations to actually remove/replace `BaseDendrite`.
Quite a few changes:
- SyncAPI accepts an `fulltext.Indexer` interface (fulltext is removed
from `BaseDendrite`)
- Caches are removed from `BaseDendrite`
- Introduces a `Router` struct (likely to change)
  - also fixes #2903
- Introduces a `sqlutil.ConnectionManager`, which should remove
`base.DatabaseConnection` later on
- probably more

relayapi/storage/storage_wasm.go

@@ -0,0 +1,42 @@
+// 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 storage
+
+import (
+	"fmt"
+
+	"github.com/matrix-org/dendrite/internal/caching"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/dendrite/relayapi/storage/sqlite3"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// NewDatabase opens a new database
+func NewDatabase(
+	conMan sqlutil.Connections,
+	dbProperties *config.DatabaseOptions,
+	cache caching.FederationCache,
+	isLocalServerName func(gomatrixserverlib.ServerName) bool,
+) (Database, error) {
+	switch {
+	case dbProperties.ConnectionString.IsSQLite():
+		return sqlite3.NewDatabase(conMan, dbProperties, cache, isLocalServerName)
+	case dbProperties.ConnectionString.IsPostgres():
+		return nil, fmt.Errorf("can't use Postgres implementation")
+	default:
+		return nil, fmt.Errorf("unexpected database type")
+	}
+}