Previously, we applied replacements to our schema definitions
to make them compatible with both SQLite and Postgres backends,
as the files were not fully compatible with either.
With this change, the only replacement required for SQLite has
been moved to the generator script. This adjustment ensures
compatibility by enabling auto-incrementing primary keys that
are treated as 64-bit integers by sqlc.
Certain invoices may not have a deterministic payment hash. For such
invoices we still store the payment hashes in our KV database, but we do
not have a sufficient index to retrieve them. This PR adds such index to
the SQL database that will be used during migration to retrieve payment
hashes.
