genai: func NewClient does not use opts ...option.ClientOption param

[awenborar]

Code
https://github.com/googleapis/google-cloud-go/blob/main/vertexai/genai/client.go#L47

func NewClient(ctx context.Context, projectID, location string, opts ...option.ClientOption) (*Client, error) {
	apiEndpoint := fmt.Sprintf("%s-aiplatform.googleapis.com:443", location)
	c, err := aiplatform.NewPredictionClient(ctx, option.WithEndpoint(apiEndpoint))
	if err != nil {
		return nil, err
	}
	return &Client{
		c:         c,
		projectID: projectID,
		location:  location,
	}, nil
}

Implication
The following code does not generate valid authentication:

client, err := genai.NewClient(ctx, "project_id", "region", option.WithCredentialsFile("../cred.json"))

Solution
Use the opts param

func NewClient(ctx context.Context, projectID, location string, opts ...option.ClientOption) (*Client, error) {
	apiEndpoint := fmt.Sprintf("%s-aiplatform.googleapis.com:443", location)
	opts = append(opts, option.WithEndpoint(apiEndpoint))
	c, err := aiplatform.NewPredictionClient(ctx, opts...)
	if err != nil {
		return nil, err
	}
	return &Client{
		c:         c,
		projectID: projectID,
		location:  location,
	}, nil
}

[eliben]

Thanks for the report! This should roll out in a bugfix version soon - #9166