- Downgraded target frameworks from net9.0 to net8.0 in multiple projects.
- Updated package references to older versions across various projects.
- Added and updated using directives in several files for better dependency management.
- Modified `Student` entity to make `SectionId` nullable and updated related methods.
- Introduced new migration files to reflect schema changes in the database.
- Added new `ValidationException` and `ValidationBehavior` classes for improved validation handling.
- Updated `launchUrl` in `launchSettings.json` to include `/swagger/v1`.
- Reformatted constructor parameters in `Patient.cs` for better readability.
- Removed `Sections` property from `University.cs`.
- Changed `PatientId` and `Patient` properties in `MedicalHistory.cs` to internal.