[Feature Request] Support ETSI ASiC-E signed documents (EU e-signed docs)

Description EU member states issue electronically signed documents under the eIDAS regulation. Most of these documents use the ETSI ASiC-E container with a XAdES signature. The container includes the signed document, a signature file, and a manifest. Different member states use different file exts: • .edoc in Latvia • .bdoc and .asice in Estonia • .adoc in Lithuania Paperless-ngx cannot import these documents today, which is a massive detriment for tech-forward member state users, as archiving those digital documents and viewing them easily is rather difficult (requires specialised programs, etc). The system detects them as "application/zip", and rejects them. In Latvia, for example, all documents being sent and received to/from the government are now digital. That includes school diplomas, all official correspondence, business records, etc. Proposed behaviour • Import ASiC-E documents • Store the original container withou…