A Postman collection belongs in the repository

A collection in one person’s account is not version control, is not reviewable and disappears when they leave.

$ ls api/
collection.json      # exported, committed
environments/
  local.json         # committed, no secrets
  staging.json       # committed, no secrets

# and the .gitignore line that matters
# api/environments/*.local.json

Exporting and committing means a change to the collection appears in a pull request alongside the change to the endpoint, which is the entire point. The export format is verbose JSON with ids in it, so the diffs are noisy — sorting or normalising on export helps and nothing does it automatically. Keeping secrets out of the committed environments is the discipline, and a template file with empty values is what makes that survivable.