pds-api#169 api user guide

[ramesh-maddegoda]

🗒️ Summary

Brief summary of changes if not sufficiently described by commit messages.

⚙️ Test Data and/or Report

One of the following should be included here:

• Reference to regression test included in code (preferred wherever reasonable)
• Attach test data here + outputs of tests

♻️ Related Issues

nasa-pds/pds-api#169

[jordanpadams]

updates added to this PR: https://github.com/NASA-PDS/pds-api/pull/184