accounts+db: Add sql db CreditAccount query

This commit adds a separate `CreditAccount` query to the sql db, to
incentivize not setting the balance directly, but rather instead
increase and decrease the balance by a specific amount.

We also update the sql store to use the new query function, instead of
setting the balance directly.

accounts/store_sql.go

@@ -34,6 +34,7 @@ const (
 //nolint:lll
 type SQLQueries interface {
 	AddAccountInvoice(ctx context.Context, arg sqlc.AddAccountInvoiceParams) error
+	CreditAccount(ctx context.Context, arg sqlc.CreditAccountParams) (int64, error)
 	DeleteAccount(ctx context.Context, id int64) error
 	DeleteAccountPayment(ctx context.Context, arg sqlc.DeleteAccountPaymentParams) error
 	GetAccount(ctx context.Context, id int64) (sqlc.Account, error)
@@ -396,17 +397,10 @@ func (s *SQLStore) IncreaseAccountBalance(ctx context.Context, alias AccountID,
 			return err
 		}
 
-		acct, err := db.GetAccount(ctx, id)
-		if err != nil {
-			return err
-		}
-
-		newBalance := acct.CurrentBalanceMsat + int64(amount)
-
-		_, err = db.UpdateAccountBalance(
-			ctx, sqlc.UpdateAccountBalanceParams{
-				ID:                 id,
-				CurrentBalanceMsat: newBalance,
+		_, err = db.CreditAccount(
+			ctx, sqlc.CreditAccountParams{
+				ID:     id,
+				Amount: int64(amount),
 			},
 		)
 		if err != nil {

db/sqlc/queries/accounts.sql

@@ -9,6 +9,12 @@ SET current_balance_msat = $1
 WHERE id = $2
 RETURNING id;
 
+-- name: CreditAccount :one
+UPDATE accounts
+SET current_balance_msat = current_balance_msat + sqlc.arg(amount)
+WHERE id = $1
+RETURNING id;
+
 -- name: UpdateAccountExpiry :one
 UPDATE accounts
 SET expiration = $1