Add support for Emergency Access (#1000)

* Add support for Emergency Access

* Add migration script

* Review comments

* Ensure grantor has premium when inviting new grantees.

* Resolve review comments

* Remove two factor references

src/Core/Models/Api/Request/EmergencyAccessRequstModels.cs

@@ -0,0 +1,47 @@
+using System.ComponentModel.DataAnnotations;
+using Bit.Core.Models.Table;
+
+namespace Bit.Core.Models.Api.Request
+{
+    public class EmergencyAccessInviteRequestModel
+    {
+        [Required]
+        [EmailAddress]
+        [StringLength(50)]
+        public string Email { get; set; }
+        [Required]
+        public Enums.EmergencyAccessType? Type { get; set; }
+        [Required]
+        public int WaitTimeDays { get; set; }
+    }
+
+    public class EmergencyAccessUpdateRequestModel
+    {
+        [Required]
+        public Enums.EmergencyAccessType Type { get; set; }
+        [Required]
+        public int WaitTimeDays { get; set; }
+        public string KeyEncrypted { get; set; }
+
+        public EmergencyAccess ToEmergencyAccess(EmergencyAccess existingEmergencyAccess)
+        {
+            // Ensure we only set keys for a confirmed emergency access.
+            if (!string.IsNullOrWhiteSpace(existingEmergencyAccess.KeyEncrypted) && !string.IsNullOrWhiteSpace(KeyEncrypted))
+            {
+                existingEmergencyAccess.KeyEncrypted = KeyEncrypted;
+            }
+            existingEmergencyAccess.Type = Type;
+            existingEmergencyAccess.WaitTimeDays = WaitTimeDays;
+            return existingEmergencyAccess;
+        }
+    }
+
+    public class EmergencyAccessPasswordRequestModel
+    {
+        [Required]
+        [StringLength(300)]
+        public string NewMasterPasswordHash { get; set; }
+        [Required]
+        public string Key { get; set; }
+    }
+}