Commented refs are collected per file and resolved against the combined
model after all inputs are loaded (directory, --from-list, merge, jobs).
Matched refs become FKs and relationships; duplicates of existing FKs are
skipped; missing targets are skipped with a warning; column type
mismatches warn.
Also keep reused index names within a DBML table instead of overwriting,
give a second FK to the same table a distinct relationship name, and make
the pgsql writer match relationships to FKs by name first.
PostgreSQL index names share the schema-wide relation namespace, so a
reused name makes CREATE INDEX IF NOT EXISTS silently skip the duplicate.
Add duplicate_index_name rule (enforce by default) covering indexes and
PK/unique constraint backing indexes.
warkanum