A new v2 API endpoint for triggering pipelines via API is now available to all organizations that integrate through GitHub (GitHub OAuth and GitHub App) and Bitbucket (Cloud and Data Center). This functionality is not yet available to organizations that integrate through GitLab.
The endpoint is:
POST /api/v2/project/{provider}/{organization}/{project}/pipeline/run
This is now the recommended API to be used to trigger pipelines.
The pre-existing endpoint for triggering new pipelines - which is only available to organizations integrating through GitHub oAuth or Bitbucket Cloud - continues to be supported.