Add `/reject` order

[jbesraa]

Is your feature request related to a problem? Please describe.
Yes. For the following scenario:

1. User 1 post a sell order
2. User 2 ask to take sell order
3. User 1 want to reject User 2 based on their reputation and time using the bot

Currently this is only possible if User 1 wait 15 minutes. The problem with waiting 15 minutes:

1. Other users making sell orders benefit from the fact that User 1 order is not listed(can be used as an attack)
2. Order is removed from the list after 15 minutes and User 1 need to re-post

Describe the solution you'd like
Add /reject action for User 1 which will result in:

1. Expire the invoice the bot sent to User 1
2. Re-post order from User 1

[Luquitasjeffrey]

Hi @grunch, can i take this issue?

[Catrya]

Hi @Luquitasjeffrey i assigned it to you