Add check operation

[adnankobir]

This PR adds the functionality to check a given lock in a pool and block/wait until that lock becomes unclaimed.
The rational behind it is as follows:

Given that we have multiple disparate pipelines that may trigger in any order:

• we would like a build pipeline to be able to claim the lock for the duration of a number of tasks (e.g Docker build/push) and release the lock afterwards
• the second (or multiple) deploy pipeline should wait until the build pipeline is completed before proceeding to pull in the updated output (ie. the Docker image built in build pipeline)

The intent is to have the deploy pipelines always use the latest available output (Docker image), and if there is an active build taking place to produce said output (Docker image), then we want to wait/block until that output is ready/published.

Now we could simply use acquire across all the pipelines, but this feel clunky since we'd end up dealing with deploy pipelines acquiring the locks unnecessarily, when all we want to do is check for existence of a claimed lock by the build pipeline only. This is especially true in cases of many:1 dependency in pipelines - we want to avoid hundreds of pipelines trying to acquire a lock unnecessarily.

check details in docs:

• check: If set, we will check for an existing claimed lock in the pool and wait until it becomes unclaimed.

  • If there is an existing lock in claimed state: wait until lock is unclaimed
  • If there is an existing lock in unclaimed state: no-op
  • If no lock exists: fail

  The purpose is to simply block until a given lock in a pool is moved from a
  claimed state to an unclaimed state. This functionality allows us to build
  dependencies between disparate pipelines without the need to acquire locks.

  Note: the lock must be present to perform a check. In other words, a get
  step to fetch metadata about the lock is necessary before a put step can
  check the existence of the lock.

Thanks in advance for the review!

cc @xtremerui

[taylorsilva]

Late but I'll take a look at this. Feels like a useful feature for this resource

[taylorsilva]

This looks good! Just some nits

[taylorsilva]

decided to just commit my nits and approve this. Thanks for the PR!

[taylorsilva]

and of course the tests fail. I'm gonna approve this PR and make my own to fix the tests since that's a mess I made 😅