Validate that submitted applications point to a valid resume

Right now the client may submit an application where the resume field doesn't identify an actual resume. We need to confirm that the resume exists

Start by tracing the application submission path and locating how the resume field is handled. Confirm what represents a valid resume, then verify that submissions referencing a missing or invalid resume are rejected and valid applications still succeed.

索引モデルが issue の本文から書いたものです。