API documentation for ATBC API and Code refactoring PD/PPD

@Jason Who should take this on- Is this you?

**Describe the task**
Currently, we are not aware of all the responses returned by the ATBC API while applying for PD status. It is required to understand the different responses and also the errors returned by ATBC.
Right now we receive the below object as a response but we do not have further information about the possible information and how to handle it. For instance, are there different types of codes that can indicate different errors?


**Questions**
- Get the information from ATBC about the possible return information from the request PD.

No source file, test, or entry point is identified. Start by reviewing the PD request and the ATBC API response information referenced in the issue, then clarify the PD/PPD refactoring scope; done means documenting the possible responses and errors and how they should be handled.

Written by the indexing model from the issue text.