BigQueryJsonDataWriter never closes when using BigQueryTemplate.writeJsonStream() about spring-cloud-gcp

[burkedavison]

Hello @deionalims - thank you for your bug report. I agree, the writer should be closed and have put up a PR to fix it.

Also, the BigQueryJsonDataWriter is instantiated every time a call to BigQueryTemplate.writeJsonStream() is made. As I make several calls to BigQueryTemplate.writeJsonStream() in my application, wouldn't it be more efficient to instantiate it once and give the control to the user to close it when needed ?

While different design decisions could've been made when creating this module, it's now important that we maintain the existing contract to avoid introducing breaking changes. Also - introducing a writer that can be reused opens the possibility of user error if they attempt to write to a different parent table, and raises potential multithreaded concerns.