Use OPA to enforce policy on command

[olegsu]

• OPA can be used to configure ACL (access control list)
• OPA can be used to configure where the command should be executed on
  • fork pr
  • regular pr
  • issue
• Unknown requirements

To define what is the input to the evaluation function, we should add "scopes" to tell the remote server what information to load, for example:

• Issue
• Pull Request
• Repo contributors
• etc

[olegsu]

/pr-bot label feature-request