scripts: add sql slices workaround to sqlc gen script

This copies the workaround introduced in the taproot-assets code base
and will allow us to use `WHERE x in <list>` type queries.

sqldb/sqlc/db_custom.go

@@ -0,0 +1,39 @@
+package sqlc
+
+import (
+	"fmt"
+	"strings"
+)
+
+// makeQueryParams generates a string of query parameters for a SQL query. It is
+// meant to replace the `?` placeholders in a SQL query with numbered parameters
+// like `$1`, `$2`, etc. This is required for the sqlc /*SLICE:<field_name>*/
+// workaround. See scripts/gen_sqlc_docker.sh for more details.
+func makeQueryParams(numTotalArgs, numListArgs int) string {
+	if numListArgs == 0 {
+		return ""
+	}
+
+	var b strings.Builder
+
+	// Pre-allocate a rough estimation of the buffer size to avoid
+	// re-allocations. A parameter like $1000, takes 6 bytes.
+	b.Grow(numListArgs * 6)
+
+	diff := numTotalArgs - numListArgs
+	for i := 0; i < numListArgs; i++ {
+		if i > 0 {
+			// We don't need to check the error here because the
+			// WriteString method of strings.Builder always returns
+			// nil.
+			_, _ = b.WriteString(",")
+		}
+
+		// We don't need to check the error here because the
+		// Write method (called by fmt.Fprintf) of strings.Builder
+		// always returns nil.
+		_, _ = fmt.Fprintf(&b, "$%d", i+diff+1)
+	}
+
+	return b.String()
+}