Write overview of technical implementation of callback API

[baltes]

As a DOCMP team member, I need a means of sending the status import attempts into PEGA back to VA.gov so that VA.gov has status information about documents sent to PEGA.

Acceptance criteria

• There is a document to guide discussion with OCTO platform team members so that they understand our architecture and design
• Share with OCTO engineering in order to get input
• Bring updated documentation to Platform Security office hours
• Share with Robbie Holmes for feedback

Placeholder file in github: https://github.com/department-of-veterans-affairs/va.gov-team/blob/master/products/health-care/champva/callback-api-technical-spec.md

[baltes]

This story is for taking technical implementation details out of the ADR and capturing them in a separate document.

[balexandr]

@baltes I moved the implementation into it's own file (you posted above) and will be updating it as a living document so people can see what columns exist, validations set, and overall structure

[cloudmagic80]

@balexandr The link to the document doesn't work

[baltes]

@balexandr @cloudmagic80 added the md extension to the filename in the link, see if that helps.

[balexandr]

@baltes Approved by Robbie

[balexandr]

Waiting for approval by someone from the security team as Gary is OOO.

[balexandr]

@baltes Kyle Crockett approved.