Custom sync task - Roadmap

[bomoko]

Presently, we have several hard coded drush tasks for doing syncs of databases across environments. This creates some issues as documented in, for example, #1786.

This issue is a roadmap and thread for discussion for how we are addressing this issue.

This is the current roadmap

1. Get custom arguments into Lagoon - this allows us to pass through arguments (such as environment names) to custom arguments. This will allow us to write, for example, sync tasks with drop-downs listing environments from which we're copying from/to.
2. Add fact filters to tasks for environment task resolution - this will allow us to specify, at custom task creation time, which environments the task should apply to (for instance, only allow a particular task to run on Drupal or Laravel sites).
3. Write a generic Lagoon-sync task. This will be a generic DB/Files tasks that should apply to almost all environments, and act as a replacement for the current hardcoded Drush tasks.