Issue Summary

Yaml generated from a Bamboo plan that has artifact download task (in UI) isn't valid when it's used in a specs repo. artifact-download tasks is missing source-plan attribute.

Specs scan fails with an error: Unknown task type artifact-download

Steps to Reproduce

1. Create a plan with artifact download task (can be all artifacts or a specific one) which download artifacts from same plan
2. Export as YAML
3. Use yaml in bamboo-specs/bamboo.yaml and create a specs repository with it

---
version: 2
plan:
  project-key: VARS
  key: GIT
  name: git
stages:
- Default Stage:
    manual: false
    final: false
    jobs:
    - Default Job
Default Job:
  key: JOB1
  tasks:
  - checkout:
      force-clean-build: 'false'
  - script:
      interpreter: SHELL
      scripts:
      - echo "Hello" > hello.md
  - artifact-download:
      artifacts:
      - name: artifact
  artifacts:
  - name: artifact
    pattern: hello.md
    shared: true
    required: true

Expected Results

Specs scan is successful

Actual Results

14-Oct-2020 06:26:03	Bamboo YAML import failed: Document structure is incorrect: Default Job / tasks / [2]: Unknown task type artifact-download

Workaround

Add source-plan to artifact-download task since it's missing when YAML export happens.