Create custom merge checks / branch restrictions

Some users would like to be able to create custom merge checks for Bitbucket Cloud, either for integrations like Code Reports, or for developers to write their own custom merge check modules.

ex. 

• Link

Update:

• Possibility to add branch restrictions to tags, making it possible to both:
  1. Set if it is necessary to have a given tag pattern
  2. Set how deep on the last commits the tag needs to be

Update #2:

• Custom merge check to allow the merge to happen only when the corresponding jira ticket is in a certain state (i.e. Ready for deployment state).