Extract keyPrefix decoding into field in RedisKvStore

export class RedisKvStore implements KvStore {

  #redis: Redis | Cluster;

  #keyPrefix: RedisKey;

  #keyPrefixStr: string;

  #codec: Codec;

  #textEncoder = new TextEncoder();

  constructor(redis: Redis | Cluster, options: RedisKvStoreOptions = {}) {

    this.#redis = redis;

    this.#keyPrefix = options.keyPrefix ?? "fedify::";

    this.#keyPrefixStr = typeof this.#keyPrefix === "string"

      ? this.#keyPrefix

      : new TextDecoder().decode(new Uint8Array(this.#keyPrefix));

    this.#codec = options.codec ?? new JsonCodec();

  }

  }

  #deserializeKey(redisKey: string): KvKey {

    const prefixStr = typeof this.#keyPrefix === "string"

      ? this.#keyPrefix

      : new TextDecoder().decode(new Uint8Array(this.#keyPrefix));

    const suffix = redisKey.slice(prefixStr.length);

    const suffix = redisKey.slice(this.#keyPrefixStr.length);

    return suffix.split("::").map((p) =>

      p.replaceAll("_:", ":")

    ) as unknown as KvKey;

   * @since 1.10.0

   */

  async *list(prefix?: KvKey): AsyncIterable<KvStoreListEntry> {

    const prefixKeyStr = typeof this.#keyPrefix === "string"

      ? this.#keyPrefix

      : new TextDecoder().decode(new Uint8Array(this.#keyPrefix));

    if (prefix == null || prefix.length === 0) {

      // Empty prefix: scan for all keys with the key prefix

      const pattern = `${prefixKeyStr}*`;

      const pattern = `${this.#keyPrefixStr}*`;

      let cursor = "0";

      do {