Nitpick: your JSON optimization should be avoided like the plague. The optimization you propose is NOT equivalent. The if condition will be evaluated true and executed for ANY non-empty value on the property hash_gym. This, of course, includes "false" (as string), "f", "F", "NO", whitespace or any invalid data.
Keep in mind, you're not transforming the attribute hash_gym to an optional attribute - you are basically adding both implicit and explicit behaviour on the property (if it doesn't exist, treat is as optional and assume false, if exists, you could care less on the contents and assume true). This makes API testing a nightmare, specially if you're exposing it to people outside your team.
Nitpick: your JSON optimization should be avoided like the plague. The optimization you propose is NOT equivalent. The if condition will be evaluated true and executed for ANY non-empty value on the property hash_gym. This, of course, includes "false" (as string), "f", "F", "NO", whitespace or any invalid data.
Keep in mind, you're not transforming the attribute hash_gym to an optional attribute - you are basically adding both implicit and explicit behaviour on the property (if it doesn't exist, treat is as optional and assume false, if exists, you could care less on the contents and assume true). This makes API testing a nightmare, specially if you're exposing it to people outside your team.