Type/Provider docker_stack should support passing flags to docker stack deploy

[jacksgt]

Use Case

The type/provider docker_stack does not support various flags for docker stack deploy, unlike the now deprecated define docker::stack:

define docker::stack(
  Optional[Pattern[/^present$|^absent$/]] $ensure                = 'present',
  Optional[String] $stack_name                                   = undef,
  Optional[String] $bundle_file                                  = undef,
  Optional[Array] $compose_files                                 = undef,
  Optional[Boolean] $prune                                       = false,
  Optional[Boolean] $with_registry_auth                          = false,
  Optional[Pattern[/^always$|^changed$|^never$/]] $resolve_image = undef,
)

Flags such as --with-registry-auth therefore not be passed to docker.

Here is the full list of Flags supported by Docker:

Usage:  docker stack deploy [OPTIONS] STACK

Deploy a new stack or update an existing stack

Aliases:
  deploy, up

Options:
      --bundle-file string     Path to a Distributed Application Bundle file
  -c, --compose-file strings   Path to a Compose file, or "-" to read from stdin
      --orchestrator string    Orchestrator to use (swarm|kubernetes|all)
      --prune                  Prune services that are no longer referenced
      --resolve-image string   Query the registry to resolve image digest and supported platforms ("always"|"changed"|"never") (default "always")
      --with-registry-auth     Send registry authentication details to Swarm agents

Describe the Solution You Would Like

These flags should be implemented as parameters in https://github.com/puppetlabs/puppetlabs-docker/blob/master/lib/puppet/provider/docker_stack/ruby.rb

Alternatively, just taking an arbitrary parameter such as extra_flags which then gets appended to the generated flags is also a possibility.

[jacksgt]

I'm sorry, after checking the source code (and trying to implement the above mentioned solution), I realized that the functionality is actually present, just the documentation a bit lacking.

docker_stack { 'test':
  compose_files => ['/tmp/docker-compose.yml'],
  ensure  => present,
  up_args => '--with-registry-auth',
}

I have therefore submitted a PR clarifying the usage of the docker stack type as well as fixing the link in the README: https://github.com/puppetlabs/puppetlabs-docker/pull/537/files