Start extracting mandate and mandate editing from positions page

[ManneG]

Closes #571

[ManneG]

What is left to do right now:

• Redo the contents and styling of the mandate editing "tooltip"
• Add a page at (app)/positions to get an overview, add, and mark positions as active/inactive
• perhaps expose deleting positions but make it clear this is not something that should usually be done as old positions should still exist in the database. This would be if you mistakenly created a post. Maybe only be able to delete posts with no people in them
• add calls to update groups in Authentik when posts are created

[ManneG]

I have made some good progress

What is left to do right now:

• Redo the contents and styling of the mandate editing "tooltip"
• ponder if positions should be able to be created in the overview (Daniel said we have a syncing script that should be fixed, I thought this was the main thing with this issue but perhaps not)
• review Anahita's changes Made design less ugly #898 to editing mandates as that will conflict with my changes.
• there are some bugs, something not updating correctly in the database (thought I fixed this but I found the bug happening again)

[RufusKoggRojder]

LGTM 👍