implement recursive channel query

crates/collab/migrations.sqlite/20221109000000_test_schema.sql

@@ -187,7 +187,6 @@ CREATE INDEX "index_followers_on_room_id" ON "followers" ("room_id");
 
 CREATE TABLE "channels" (
     "id" INTEGER PRIMARY KEY AUTOINCREMENT,
-    -- "id_path" TEXT NOT NULL,
     "name" VARCHAR NOT NULL,
     "room_id" INTEGER REFERENCES rooms (id) ON DELETE SET NULL,
     "created_at" TIMESTAMP NOT NULL DEFAULT now
@@ -199,8 +198,6 @@ CREATE TABLE "channel_parents" (
     PRIMARY KEY(child_id, parent_id)
 );
 
--- CREATE UNIQUE INDEX "index_channels_on_id_path" ON "channels" ("id_path");
-
 CREATE TABLE "channel_members" (
     "id" INTEGER PRIMARY KEY AUTOINCREMENT,
     "channel_id" INTEGER NOT NULL REFERENCES channels (id) ON DELETE CASCADE,