feat(structure): structure attachment validation can be mandatory

If choosen in setting, user set structure can be placed under mandatory validation

- add "awaitingStructure" prop to user schema, which will hold an "_id"
- add "userStructureValidationMandatory" to appsettings schema, which hold a bool
- update "setStructure" (and its tests) to match new logic
- add "acceptAwaitingStructure" method to validate user when it's mandatory
- refactor "AdminUserValidationPage" so that it use an extracted component "AdminUserValidationTable"
- update "ProfilePage" so its shows if a structure is awaited
- update menu layout to show admin validation page, and nb of awaiting users