Improve User Maintenance

[barthel-eu]

Feature Request: Transform pommo_subscriber_data into a flat table, preferably merged with pommo_subscribers. Optional or additional: Allow import of data overwriting existing data (incl. status!) on new import with externally updated values, keeping the same subscriber ID for the e-Mail-address.

Detail: I find it extremely hard to understand the poMMo database structure on users. Instead of fields as columns in a table, fields are given an ID and all just dumped into a file. That makes it impossible or at least very difficult to manage mailing lists, all other contact databases we use enjoy "flat" tables that can be exported to Excel. There's no export. On the import, I cannot give an "updated" file that contains the updates - I cannot overwrite existing users keeping their poMMo user ID, I cannot change status, where subscribers unsubscribe by "remove"-reply and not via URL or where the users simply return an error that bounces to the mail account (undeliverable mail). With a "new" import, I get new "pommo subscriber IDs", making it impossible to use a "landing page" needed for KPIs beyond the next mailing, as I cannot "specify" the subscriber-ID on import.