Remove monthly_supporter from user endpoints except users/me

[kueda]

Currently we're including the monthly_supporter attribute at https://api.inaturalist.org/v2/users/1?fields=all (and maybe at other endpoints?). That describes whether the user is a monthly supporter, but we also have an opt-in preference to control whether this information is displayed, implying that it's at least somewhat secret. So I suggest we

• Remove monthly_supporter from all endpoints other than users/me
• Add monthly_supporter_badge to GET /users/:id that is the value or user.prefers_monthly_supporter_badge && user.monthly_supporter

The goal is for clients like iNat Next to show a badge for people who are donors and want to show it.

[kvangork]

@kueda Will our existing apps cleanly handle monthly_supporter disappearing from responses?
If not, or if we're unsure how other code will react, we could leave it in place but change the response value so that it returns the true status if :id == me but otherwise respects the logic you proposed for the monthly_supporter_badge

[kueda]

@budowski and @alexshepard will have a more informed opinion, but neither of the legacy app repos make direct reference to monthly_supporter.

[budowski]

Yeah, like @kueda said, Android doesn't make use of that property - we could leave that property on for id=me like @kvangork suggested, if we plan on displaying that badge inside the app somewhere.

[alexshepard]

We don't map this from json, so the legacy iOS app wont notice if it goes away.