Expense receipt file storage via third-party storage provider like Amazon S3 or Cloudflare R2

[HappyEarthDay]

Describe the problem

Almost every expense-tracking system has a way to upload proof of purchase (receipts). Kimai currently doesn't have this and it's the one thing I think this amazing platform is missing. We have to store our receipts in a separate system and manually make sure the names of the expenses in Kimai match the name of the receipt file, which creates a lot of work.

Describe the solution you'd like

It could become problematic to host the files locally on the Kimai instance due to cloud storage costs and additional reconfiguration of existing systems. It seems totally logical to rely on third-party storage solutions like Amazon S3 or Cloudflare R2, which both offer very generous free tiers which would suit the needs of most organizations using Kimai.

Under Settings < Expenses, we'd love an optional setting to configure the authentication method to a third party storage provider. When this is configured, an additional attachment field would be available when creating or editing expenses, and it uploads the file to the third party storage provider.

Receipts should be limited to file types like PDF, JPG, PNG and similar formats.

Describe alternatives you've considered

Having the receipts hosted on the Kimai instance would be great for the user, but maybe would increase the hosting complexity of the hosting configuration and maybe not worth it for the scalability.

Screenshots

No response