made models and added composite primary key to userCohort in dataContext

exercise.wwwapi/Data/DataContext.cs

@@ -20,6 +20,11 @@ protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
         protected override void OnModelCreating(ModelBuilder modelBuilder)
         {
 
+
+            modelBuilder.Entity<UserCohort>()
+                .HasKey(uc => new { uc.UserId, uc.CohortId });
+
+
             modelBuilder.Entity<User>()
                 .Property(u => u.Role)
                 .HasConversion<string>();
@@ -49,5 +54,7 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
         public DbSet<User> Users { get; set; }
         public DbSet<Post> Posts { get; set; }
         public DbSet<PostComment> PostComments { get; set; }
+        public DbSet<Cohort> Cohorts { get; set; }
+        public DbSet<UserCohort> UserCohorts { get; set; }
     }
 }

exercise.wwwapi/Models/Cohort.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace exercise.wwwapi.Models
+{
+    [Table("cohorts")]
+    public class Cohort
+    {
+        [Key, Column("id")]
+        public int Id { get; set; }
+        [Column("title")]
+        public string Title { get; set; } = string.Empty;
+    }
+}

exercise.wwwapi/Models/UserCohort.cs

@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace exercise.wwwapi.Models
+{
+    [Table("userCohorts")]
+    public class UserCohort
+    {
+        [Column("cohortid")]
+        public required int CohortId { get; set; }
+        [ForeignKey("CohortId")]
+        public Cohort? Cohort { get; set; }
+
+
+        [Column("userid")]
+        public required int UserId { get; set; }
+        [ForeignKey("UserId")]
+        public User? User { get; set; }
+    }
+}