feat: document policy allocate endpoint

[sameenfatima78]

Add a description of your changes with links to any relevant material.

Date Needed (optional)

If the release date of a feature is known or estimated, provide it to give reviewers guidance on turnaround time.

Reviewers

Possible roles follow. The PR submitter checks the boxes after each reviewer finishes and gives :+1:.

• [ ] Subject matter expert:
• [ ] Subject matter expert:
• [ ] Product review:
• [ ] Partner support:
• [ ] PM review:

FYI: Tag anyone else who might be interested in this PR here.

Testing

• [ ] Ran ./run_tests.sh without warnings or errors

HTML Version (optional)

• [ ] Build an RTD draft for your branch and add a link here

Sandbox (optional)

• [ ] Point to or build a sandbox for the software change and add a link here

Post-review

• [ ] Add a comment with the description of this change or link this PR to the next release notes task.
• [ ] Squash commits