Use pointers for Date* fields

orm/credential.go

@@ -19,8 +19,8 @@ type Credential struct {
 	PlainPassword   string
 	Email           string `csv:"email"`
 	AltEmail        string
-	DateFrom        time.Time
-	DateTo          time.Time
+	DateFrom        *time.Time
+	DateTo          *time.Time
 	TelephoneNumber string
 
 	Regenerate bool `schema:"Regenerate" sql:"default: false"`