Optional Atlantis auto_plan on transitive module dependencies

[vincenthsh]

Current

If component A depends on:

1. Modules: foo & bar
2. Components: B

And component B depends on:

1. Modules: baz

Currently fogg generates Atlantis config as follows:

projects:
- A:
    auto_plan:
    - ./
    - ../path/to/module/foo
    - ../path/to/module/bar

- B:
    auto_plan:
    - ./
    - ../path/to/module/baz

If module baz changes, component B is planned
If component B changes, component A is not planned

In some cases, when module baz or component B are changed, component A could have a diff which is not detected.

Proposal:

• Optionally, Atlantis should autoplan component A if component B has changes
• Optionally, Atlantis should autoplan component A if module baz changes

Possible issues:

1. Changes in B haven't been applied, so atlantis autoplan on A may fail, however this could be more desirable than not detecting the diff in A and in such cases either manual intervention (targetted plan/apply or split PR) should handle this until Atlantis can manage it?

Expected Atlantis config (when feature is enabled):

projects:
- A:
    auto_plan:
    - ../path/to/component/A
    - ../path/to/module/foo
    - ../path/to/module/bar
    # because A depends on B
    - ../path/to/component/B
    - ../path/to/module/baz

- B:
    auto_plan:
    - ../path/to/component/B
    - ../path/to/module/baz