@Nullable
    public String getFilename() {
        return this.filename;
    }
Return the value of the {@literal filename} parameter, possibly decoded
from BASE64 encoding based on RFC 2047, or of the {@literal filename*}
parameter, possibly decoded as defined in the RFC 5987.
manager/api/rest-impl/src/main/java/io/apiman/manager/api/rest/impl/util/ContentDisposition.java