[_] feat: allow empty files on creation and replacement

[apsantiso]

Adds support for empty files (size = 0) during file creation and replacement. Empty files now have null fileId values instead of requiring a network file identifier, reducing unnecessary network storage usage.

Changes

• Updated CreateFileDto and ReplaceFileDto to make fileId optional and conditionally required only when size > 0
• Implemented empty file limit checking via MaxZeroSizeFiles feature limit
• Updated file creation and replacement logic to set fileId = null when size = 0
• Modified file replacement lock mechanism to handle empty file scenarios:
  • Uses newFileId when replacing empty file with actual file
  • Uses oldFileId when replacing actual file with empty file
  • Falls back to uuid only when both files are empty. No usage change and no record in usages table is created as we always check if delta = 0 before creating a record in the usages table.

Depends on:
#824

[apsantiso]

Defensive lock key selection to prevent race conditions during file replacement:

Scenario 1: oldFileId exists, newFileId is null (replacing file with empty file)
- lockKey = oldFileId
- delta = oldSize - 0
- Usage replacement IS created

Scenario 2: oldFileId is null, newFileId is null (replacing empty file with empty file)
- lockKey = uuid (fallback)
- delta = 0 - 0
- NO usage replacement created (safe - no actual usage change)

Scenario 3: oldFileId is null, newFileId exists (replacing empty file with actual file)
- lockKey = newFileId
- delta = 0 - newSize
- Usage replacement IS created

I know it is somehow inconsistent but this is the only way we have (for the time being) to protect us from duplicated usage records when allowing empty files without modifying too much things, let's see if there's a better way when I take the ticket I created today @sg-gs

[apsantiso]

Scenario 2 is just a fallback as inside the service we always check if delta != 0. We never create a replacement usage record with delta = 0.

[sg-gs]

For free users, it would be a good idea to throw a 402 for the frontend (upgrade to get more features)

[larryrider]

Hey @apsantiso! Shouldn't the fileId from file.dto be modified as string | undefined too? 🤔
For what I see it should be:

• file.dto
• create-file.dto (already modified)
• replace-file.dto (already modified)

[apsantiso]

Hey @apsantiso! Shouldn't the fileId from file.dto be modified as string | undefined too? 🤔 For what I see it should be:

• file.dto
• create-file.dto (already modified)
• replace-file.dto (already modified)

True, modified @larryrider

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
82.4% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud