The previous fix only covered migration errors. The same truncation
affected two more places, both because tokio_postgres::Error's Display
prints only "db error" while the real message lives in source():
- api/error.rs: AppError::{db_conn,query,tx} logged with {e}, so every
runtime DB failure showed as "Query failed: db error". The
constructors' bound is tightened from impl Display+Debug to
impl std::error::Error so the source chain can be walked; the
user-facing message stays sanitized (existing tests still pass).
- db/pool.rs: ensure_database formatted tokio_postgres::Error directly
into the String returned to main.rs' exit(1) path, collapsing to
"failed to query pg_database: db error" etc.
Adds a shared crate::db::format_with_sources helper (walks source()
with de-dup of placeholder layers) and reuses it from MigrateError's
Display, the AppError constructors, and pool.rs.
xfy
383e6f6b43