[DEV TASK]: Implement API for Opening Details Tombstone on the backend

[paulushcgcj]

Task Summary

Implement the Tombstone and summary information API

Task Details

When the user accesses the Opening details page, the frontend will first request the most basic information for that opening to populate the tombstone information along with the base/summary information. This API should contain all the information described at #655 that will be initially loaded when the user accesses the screen.

Affected Environments

• Development
• Test
• Production

Additional Context

More details about the data will come as soon as the screen is finalized