feat: add a professor create

Application/Cqrs/Professor/Commands/CreateProfessor/CreateProfessorCommand.cs

@@ -0,0 +1,9 @@
+using MediatR;
+
+namespace Mirea.Api.DataAccess.Application.Cqrs.Professor.Commands.CreateProfessor;
+
+public class CreateProfessorCommand : IRequest<int>
+{
+    public required string Name { get; set; }
+    public string? AltName { get; set; }
+}

Application/Cqrs/Professor/Commands/CreateProfessor/CreateProfessorCommandHandler.cs

@@ -0,0 +1,30 @@
+using System.Threading;
+using System.Threading.Tasks;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using Mirea.Api.DataAccess.Application.Common.Exceptions;
+using Mirea.Api.DataAccess.Application.Interfaces.DbContexts.Schedule;
+
+namespace Mirea.Api.DataAccess.Application.Cqrs.Professor.Commands.CreateProfessor;
+
+public class CreateProfessorCommandHandler(IProfessorDbContext dbContext) : IRequestHandler<CreateProfessorCommand, int>
+{
+    public async Task<int> Handle(CreateProfessorCommand request, CancellationToken cancellationToken)
+    {
+        var entity = await dbContext.Professors.FirstOrDefaultAsync(p => p.Name == request.Name, cancellationToken: cancellationToken);
+
+        if (entity != null)
+            throw new RecordExistException(typeof(Domain.Schedule.Professor), nameof(Domain.Schedule.Professor.Name), entity.Id);
+
+        var professor = new Domain.Schedule.Professor()
+        {
+            Name = request.Name,
+            AltName = request.AltName
+        };
+
+        var result = await dbContext.Professors.AddAsync(professor, cancellationToken);
+        await dbContext.SaveChangesAsync(cancellationToken);
+
+        return result.Entity.Id;
+    }
+}