Make it (a tiny bit) easier to run your own collab (#9557)

* Allow creating channels when seeding
* Allow configuring a custom `SEED_PATH`
* Seed the database when creating/migrating it so you don't need a
  separate step for this.

Release Notes:

- N/A

crates/collab/.env.toml

@@ -1,4 +1,5 @@
 DATABASE_URL = "postgres://postgres@localhost/zed"
+# DATABASE_URL = "sqlite:////home/zed/.config/zed/db.sqlite3?mode=rwc"
 DATABASE_MAX_CONNECTIONS = 5
 HTTP_PORT = 8080
 API_TOKEN = "secret"
@@ -13,6 +14,7 @@ BLOB_STORE_BUCKET = "the-extensions-bucket"
 BLOB_STORE_URL = "http://127.0.0.1:9000"
 BLOB_STORE_REGION = "the-region"
 ZED_CLIENT_CHECKSUM_SEED = "development-checksum-seed"
+SEED_PATH = "crates/collab/seed.default.json"
 
 # CLICKHOUSE_URL = ""
 # CLICKHOUSE_USER = "default"