Allow CI_JOB_TOKEN in pipeline trigger API and/or pipeline create API

Description

Developers need to trigger cross-project pipelines from CI/CD pipeline jobs. We already have an API for this, and a way to generate tokens in the web UI, but it would be better to allow people to use the existing CI_JOB_TOKEN rather than a registered token. This would automatically respect permissions of the user triggering the pipeline.

Proposal

Links / references

Documentation blurb

(Write the start of the documentation of this feature here, include:

1. Why should someone use it; what's the underlying problem.
2. What is the solution.
3. How does someone use this

During implementation, this can then be copied and used as a starter for the documentation.)