In the mid-credit scene, we see Shazam invites Superman to his school in the lunch break.
From previous knowledge, we know that Shazam has been a part of the Justice League. But there was no cameo of any of the Justice league character in the film, and that of Superman is faceless.
Do these two films exist in the same universe under the same franchise?
Somewhere on Youtube (a review channel), I heard, Henry Cavill didn't have dates for Shazam, was that the real reason?