Opt-in contact

REQUIRED SCOPES <code>['contacts:write']</code><br> An opt-in contact means a contact being enabled for reaching out. In case a contact is currently opt-out, i.e. disabled, this request makes this contact available for communication. <br><br> As a result, the current user becomes allowed to send messages to the contact, which is also reflected with a note on the current user’s side bar.