Add a tus-js-client urlStorage implementation based on JS maps

[timabbott]

As documented in https://github.com/tus/tus-js-client/blob/main/docs/api.md#urlstorage, it should be possible to instead of disabling this bit of tusd functionality, just provide a little module that uses JS maps to implement the API that tus-js-client expects here, without using browser local storage and the security concerns that come with it.

[zulipbot]

Hello @zulip/server-misc members, this issue was labeled with the "area: uploads" label, so you may want to check it out!

[devyk100]

@zulipbot claim

[zulipbot]

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[hustlernik]

@timabbott Can I take up this issue?

[hustlernik]

@timabbott I have gone through the PS, looked into tus-js-client npm package and tus protocol.

This is how I am thinking to implement this:

The MapUrlStorage class uses JavaScript's Map to store and retrieve upload URLs for tus-js-client, following the required UrlStorage interface. Each upload is associated with a file's fingerprint, and a unique urlStorageKey is generated for each upload. This in-memory storage avoids using browser local storage, making it suitable for environments where local storage may raise security concerns.

Sample code Snippet:

class MapUrlStorage {
  constructor() {
    this.storage = new Map();
  }

  async findAllUploads() {
    return Array.from(this.storage.values()).flat();
  }

  async findUploadsByFingerprint(fingerprint) {
    return this.storage.get(fingerprint) || [];
  }

  async removeUpload(urlStorageKey) {
    for (const [fingerprint, uploads] of this.storage.entries()) {
      const updated = uploads.filter(entry => entry.urlStorageKey !== urlStorageKey);
      updated.length ? this.storage.set(fingerprint, updated) : this.storage.delete(fingerprint);
    }
  }

  async addUpload(fingerprint, upload) {
    const urlStorageKey = `upload-${Date.now()}-${Math.random().toString(36).slice(2)}`;
    const newUpload = { ...upload, urlStorageKey };
    this.storage.set(fingerprint, [...(this.storage.get(fingerprint) || []), newUpload]);
    return urlStorageKey;
  }
}