YAML Spec scan fails if the include tag files contains permission definition

Issue Summary

YAML Specs extends YAML with the !include 'file' tag. The include tag expands to the content of the file where it is placed. If the YAML files contain permission, the Specs scan will fail.

Steps to Reproduce

1.  Define multiple YAML Spec files, which contains plan permission e.g. plan1.yml and plan2.yml
2. Include the files in bamboo.yml file

   ---
   !include 'plan1.yml'
   ---
   !include 'plan2.yml'
   

Expected Results

Multiple plans should be created on Specs scan

Actual Results

Scan fails, with only one plan created, with error in log

 Invalid format of the YAML file: expected a single document in the stream

Workaround

Define each plan permission in the main bamboo.yml file, and not in each plan YAML file

---
!include 'plan1.yml'
---
!include 'plan2.yml'

---
version: 2
plan: PROJECT-PLAN1

plan-permissions:
  - users: admin
    permissions:
      - admin
  - roles: logged-in
    permissions:
      - view

---
version: 2
plan: PROJECT-PLAN2

plan-permissions:
  - users:
      - admin
    permissions:
      - view
    - roles: logged-in
    permissions:
      - view