Add schedule api (#60)

apps/web/prisma/schema.prisma

@@ -166,6 +166,7 @@ model ApiKey {
 }
 
 enum EmailStatus {
+  SCHEDULED
   QUEUED
   SENT
   DELIVERY_DELAYED
@@ -177,6 +178,7 @@ enum EmailStatus {
   CLICKED
   COMPLAINED
   FAILED
+  CANCELLED
 }
 
 model Email {
@@ -195,6 +197,7 @@ model Email {
   domainId     Int?
   createdAt    DateTime     @default(now())
   updatedAt    DateTime     @updatedAt
+  scheduledAt  DateTime?
   attachments  String?
   campaignId   String?
   contactId    String?