Only subscribe users when $sync_member_fields fields have changed

[jjjjjjjjjjjjjjjjjjjj]

I'm getting a lot of errors from MailChimp saying Recipient "[email protected]" has too many recent signup requests, since subscribe is firing on every onBeforeWrite() of a Member, and sometimes writes happen frequently.

Perhaps we could add something along the lines of this to onBeforeWrite()? To prevent API calls to MailChimp when nothing has changed.

$syncFields = array_keys(static::get_sync_member_fields());
$matches    = [0];

foreach ($syncFields as $field) {
    $matches[] = isset($changed[$field]);
}

if (!max($matches)) {
    return;
}

[camfindlay]

Happy to review a pull request if you can put it together. Would be also good to have a test to check this 👍

[jjjjjjjjjjjjjjjjjjjj]

Appreciate the immediate response! I'll look into it.

[camfindlay]

You are very welcome @janneklouman