Possible to decline multiple-user offers

[bartervg]

Describe the bug

It's possible to decline a multiple user offer. This is a contradiction since the user would need to join the offer in order to decline it.

Steps to reproduce the bug

1. Join a multiple user offer
2. Decline offer
3. Sender would need to recreate offer

Expected behavior

If the user does not want the offer, they should click not interested, or if they've joined the offer, leave the offer. In addition, there should be more tools to manage multiple user offers, both for the senders and potential recipients.

Screenshots

Reported example https://barter.vg/u/7cfa/o/5028643/

[bartervg]

More offer issues, as discussed on Discord

• don't even show multiple user offers to ignored users (I thought this was an old fix)
• time limit after joining an offer
• kick button for offer sender
• offer accept lock
• invite to offer / friend-only
• spin-off / easier-to-create offer