Default to users being opted out of being shown on the map

[dparker1005]

When a user checks out on the website, if the purchase included a billing address, their location pin will then immediately show on the Membership Map without notifying the user or giving them the option to opt out beforehand.

Although the exact address isn't shared, showing a user's map marker without explicit content sounds like a privacy issue that we should look into. We should consider making the membership map an opt-in feature instead of an opt-out feature to ensure that we have users' consent.

[dparker1005]

Related to #74