Add ItemCollection fragment #25

[m-mohr]

Related Issue(s): #25

Proposed Changes:

1. Add ItemCollection fragment back in

PR Checklist:

• This PR is made against the dev branch (all proposed changes except releases should be against dev, not master).
• This PR has no breaking changes.
• I have added my changes to the CHANGELOG or a CHANGELOG entry is not required.
• OpenAPI files only: I have run npm run generate-all to update the generated OpenAPI files.