Clear the confusion in user story
The requirement is : Message creator submits message and then the notification goes to reviewer who reviews the message.
Now, 1st user story is about : Message creator submits message.
2nd user story is about : Reviewer gets the notification
As a Reviewer
I should get a notification when a Message writer submits a message
So that I can review the message
My question is : can we simply avoid second user story and mention the requirement under acceptance criteria of first user story?
For example, one of the acceptance criteria of first user story would be :
If user clicks on “SUBMIT” without filling all the mandatory fields, appropriate message should be shown to user and notification should go to reviewer.
My other question is where should we mention the standard format of notification content ?
It depends on the Size of the story or PBI. Your team should be able to complete it within a Sprint. You can use the Acceptance criteria for notification content.