query: add query prepare method

Author: Kulezi

query.go

@@ -19,6 +19,18 @@ type Query struct {
 	retryPolicy transport.RetryPolicy
 }
 
+func (q *Query) Prepare(ctx context.Context) error {
+	p, err := q.session.prepareStatement(ctx, q.stmt)
+	if err != nil {
+		return err
+	}
+
+	q.stmt = p.stmt
+	q.exec = p.exec
+	q.asyncExec = p.asyncExec
+	return nil
+}
+
 func (q *Query) Exec(ctx context.Context) (Result, error) {
 	info, err := q.info()
 	if err != nil {

session.go

@@ -161,7 +161,10 @@ func (s *Session) Query(content string) Query {
 
 func (s *Session) Prepare(ctx context.Context, content string) (Query, error) {
 	stmt := transport.Statement{Content: content, Consistency: frame.ALL}
+	return s.prepareStatement(ctx, stmt)
+}
 
+func (s *Session) prepareStatement(ctx context.Context, stmt transport.Statement) (Query, error) {
 	// Prepare on all nodes concurrently.
 	nodes := s.cluster.Topology().Nodes
 	resStmt := make([]transport.Statement, len(nodes))