Implement backend topic import

[luisa-beerboom]

Apart from the normal feature branches, this very specifically needs OpenSlides/openslides-backend#1697 in order to work properly.

[rrenkert]

• In the fullscreen preview dialog the row content does not fit the table header:
  

• Closing this dialog clears the embedded table.

• The preview should disappear after successful import (offer a navigation to the agenda?)

[rrenkert]

• In full screen the columns "title", "text", and "comment" should use kind of dynamic width.
• After performing an initial import a dialog "Stopped waiting for process(es)" comes up. Refreshing the list view shows all imported items.
• After perfoming an import the user can select a new file to import, but no new preview is shown.

[rrenkert]

• In full screen the columns "title", "text", and "comment" should use kind of dynamic width.
• After performing an initial import a dialog "Stopped waiting for process(es)" comes up. Refreshing the list view shows all imported items.
• After perfoming an import the user can select a new file to import, but no new preview is shown.

[luisa-beerboom]

• In full screen the columns "title", "text", and "comment" should use kind of dynamic width.

  • After performing an initial import a dialog "Stopped waiting for process(es)" comes up. Refreshing the list view shows all imported items.

  • After perfoming an import the user can select a new file to import, but no new preview is shown.

I only fixed the first one, as I can't replicate the others. Are you sure that your instance is working correctly @rrenkert ?

[rrenkert]

Looks good so far.

Some minor things:

• Importing duplicated topics shows a misleading tooltip "Duplizieren" for the warning icon.
• After a successful import the summary shows

Total topics: 19
Topics with warnings (will be skipped): 19

better would be

Total topics: 19
Topics skipped: 17
Topics created: 2

I only fixed the first one, as I can't replicate the others. Are you sure that your instance is working correctly @rrenkert ?

I can still replicate the one with the second file upload:

• select a file and perform the import.
• select the same file again -> nothing happens.

[rrenkert]

please see my last comment.

[luisa-beerboom]

Fixed some stuff, if the second file upload thing still happens, please give a better description

[rrenkert]

Additional info for the second file upload: Happens in Chromium based browsers.

Another point: When selecting a file for upload a scrollbar appears in the upper card.

[bastianjoel]

Not entirely sure but afaik our linter should complain about inline style definitions. Use a class instead if possible.

[rrenkert]

Works as expected now.