* fixed attachment statistics for sqlite
* Split attachment path into internal and external path, so the external source URL can be retained after a file is downloaded
* Make internal and external path for attachments nullable, to make clear that they have no internal or external path
* Added migrations for nullable columns for postgres and mysql
* Added migration for nullable internal and external pathes for sqlite
* Added translations
* Fixed upload error
* Restrict length of filename badge in attachment edit view
* Improved margins with badges in attachment edit
* Added a link to view external version from attachment edit
* Let media_url stay in API attachments responses for backward compatibility
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Co-authored-by: jona <a@b.c>
Co-authored-by: Jan Böhmer <mail@jan-boehmer.de>
