[WIP] Add option to cancel a build

this is a rough draft, I'm actively working on it.. so it may throw errors and it may have dirty code.

   - Add cancelling and cancelled status for builds
   - Remove pod and update builds to cancelled when a cancel event was triggered for the build
I will use the 2 `l` version aka British version, because we saw Kubernetes use it this way, if it's ok with you also.