GraphQL: Add missing fields (#20646)

Went through the model and added all missing fields.

Except user.Password/MfaSecret/AuthData and session.TeamMembers.

```release-note
NONE
```

model/session.go

@@ -244,3 +244,7 @@ func (s *Session) CreateAt_() float64 {
 func (s *Session) ExpiresAt_() float64 {
 	return float64(s.ExpiresAt)
 }
+
+func (s *Session) LastActivityAt_() float64 {
+	return float64(s.LastActivityAt)
+}