sqldb: add invoice event queries

sqldb/sqlc/queries/invoice_events.sql

@@ -0,0 +1,35 @@
+-- name: InsertInvoiceEvent :exec
+INSERT INTO invoice_events (
+    created_at, invoice_id, htlc_id, set_id, event_type, event_metadata
+) VALUES (
+    $1, $2, $3, $4, $5, $6
+);
+
+-- name: SelectInvoiceEvents :many
+SELECT *
+FROM invoice_events
+WHERE (
+    invoice_id = sqlc.narg('invoice_id') OR 
+    sqlc.narg('invoice_id') IS NULL
+) AND (
+    htlc_id = sqlc.narg('htlc_id') OR 
+    sqlc.narg('htlc_id') IS NULL
+) AND (
+    set_id = sqlc.narg('set_id') OR 
+    sqlc.narg('set_id') IS NULL
+) AND (
+    event_type = sqlc.narg('event_type') OR 
+    sqlc.narg('event_type') IS NULL
+) AND (
+    created_at >= sqlc.narg('created_after') OR 
+    sqlc.narg('created_after') IS NULL
+) AND (
+    created_at <= sqlc.narg('created_before') OR 
+    sqlc.narg('created_before') IS NULL
+) 
+LIMIT @num_limit OFFSET @num_offset;
+
+-- name: DeleteInvoiceEvents :exec
+DELETE
+FROM invoice_events
+WHERE invoice_id = $1;