[Crowdfund] Allow owner to end/pause the campaign

[cowboy0015]

Description

The owner can end/pause the campaign which is on ONGOING stage.

Implementation

• The campaign fails if it did not hit the soft capital and is expired
• The campaign is successful if it is not failed
• The fund should be sent to the withdrawal address if it is successful
• [WIP] Additional cases to end the campaign (Not by the owner)
  • Purchasing tier(which fails) once the campaign is expired should trigger to end the campaign?
• Owner can not end the campaign if it is not expired and did not hit the soft capital yet
  • [WIP] Should we allow end campaign in this case if no tiers are purchased yet for pausing the campaign?

Dependencies

ANDC-88

Acceptance Criteria

• Owner can stop the campaign when the soft capital is hitted or when it is expired
• In case the campaign is successful, gained capital should be sent to the withdrawal address
• Unit tests