Fix nullable

GerbilManagerWebAPI/Models/Gerbil.cs

@@ -5,10 +5,10 @@ namespace GerbilManagerWebAPI.Models
     public record Gerbil
     {
         [Key]
-        public Guid Id { get; init; }
-        public required string Name { get; init; }
-        public Gender Gender { get; init; }
-        public Litter? Litter { get; set; }
-        public Breeder? Breeder { get; set; }
+        public Guid Id { get; init; } // init => properties are immutable by default, they are only mutable in the constructor and initializer.
+        public required string Name { get; set; } //required => parameter is necessary in constructor and object iniilization list. So it cannot be intantiated without it
+        public required Gender Gender { get; set; }
+        public Litter? Litter { get; set; } // Any variable where the ? isn't appended to the type name is a non-nullable reference type.
+        public Breeder? Breeder { get; set; } // You use the null-forgiving operator ! following a variable name to force the null-state to be not-null. For example, if you know the name variable isn't null but the compiler issues a warning, you can write the following code to override the compiler's analysis:
     }
 }