Add organisation guids to case studies links hash.
Add organisations to case_study JSON schema.
Push all case studies to publishing API again.
Verify case study with orgs JSON is valid

Just some extra safety to make sure we're producing valid JSON.
content_id should be lowercase
Correct pattern for content_ids

See https://github.com/alphagov/content-store/blob/master/app/validators/uuid_validator.rb
Merge pull request #1851 from alphagov/orgs_in_case_studies

Add organisations to case studies content-store json.