663-AccessTokens validate expiration date (#3104)

* 663-AccessTokens validate expiration date

* removing unecessary using statement

* thomas' suggested change

* Thomas' suggested change

* Update src/Api/SecretsManager/Models/Request/AccessTokenCreateRequestModel.cs

Co-authored-by: Thomas Avery <43214426+Thomas-Avery@users.noreply.github.com>

---------

Co-authored-by: Thomas Avery <43214426+Thomas-Avery@users.noreply.github.com>

src/Api/SecretsManager/Models/Request/AccessTokenCreateRequestModel.cs

@@ -4,7 +4,7 @@ using Bit.Core.Utilities;
 
 namespace Bit.Api.SecretsManager.Models.Request;
 
-public class AccessTokenCreateRequestModel
+public class AccessTokenCreateRequestModel : IValidatableObject
 {
     [Required]
     [EncryptedString]
@@ -34,4 +34,13 @@ public class AccessTokenCreateRequestModel
             EncryptedPayload = EncryptedPayload,
         };
     }
+
+    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
+    {
+        if (ExpireAt != null && ExpireAt <= DateTime.UtcNow)
+        {
+            yield return new ValidationResult(
+               $"Please select an expiration date that is in the future.");
+        }
+    }
 }