[Feature Request] New Custom Field Type: Choose with Complex Type

Description Problem Statement Paperless-ngx already has a custom field called "Choose" where a value can be selected from a fixed list. While this is very convenient for use within Paperless-ngx, it has significant limitations when the custom field is used in the template for the storage path. Currently, it's only possible to access the value as it appears in Paperless-ngx. Use Case I want to define a fixed list of values ​​for a custom field (for example, "Contract" or "Vacation Trip") so that it can be assigned to documents (similar to the existing „Choose“ field). In addition to the actual display name, it should be possible to assign additional fixed metadata (a kind of inherited custom field) that I can access, among other things, in the template mechanism. I would like to use this, for example, for documents that I can assign to specific contracts or vacation trips. These documents should have their own subfolder in the file syst…