[Feature Request] Add a new consumption scope in paperless mail

Description I’ve been using Paperless for a while now and recently set up automatic email processing. However, due to the nature of the emails I receive, I’ve had to implement a workaround: I want to import emails from one account separately, depending on whether they have an attachment or not. I receive invoices either as attachments or as the body of the email. At the moment, I sort these into separate folders and import them using separate email rules. As a new feature, I would suggest introducing a new ConsumptionScope that works as follows: - If an email contains attachments, import the attachments - If an email does not contain any attachments, import the .eml file I created a fork and a branch there where I made adjustments to the data I found. However, I'm not very familiar with Django, so I don't know if any other files need to be changed. I created a fork and a branch where I modified the data I found. However, I'm not very familiar with Django…