feat: use Primary location unless location is set explicitly

[joker1007]

BigQuery can switch dataset location.

Unless location field is set explicity, current embulk-output-bigquery use us/eu location implicitly.
But, BigQuery can insert to any location without location information, and return location information in job_reference field.
And so, I make embulk-output-bigquery enable to use returned location information, if location config is not set.

This patch eliminates the need to change embulk config when switching location

[joker1007]

@hiroyuki-sato could you review this?

[hiroyuki-sato]

@joker1007, I'm sorry for not getting back to you sooner.

Looking good to me. I want to ask some questions just in case.

1. Does Primary locations (_response.job_reference.location ) mean it contains other places neither us nor eu ? (ex: asia-northeast1?) JobReference
2. This change keeps the current behavior except the log message. correct?

Below is my memo.

This PR changes the log message from in us/eu to in Primary location.

2024-12-16 20:36:11.397 +0900 [INFO] (Ruby-0-Thread-2: /path/to/embulk-output-bigquery-0.7.1/lib/embulk/output/bigquery/bigquery_client.rb:153): embulk-output-bigquery: Load job starting... job_id:[embulk_load_job_d63fa73e-09b5-4a57-877e-bf934b3638d4] /var/folders/c4/n95yngmn1kz96x7jslsnqjr80000gn/T/embulk_output_bigquery_20241216-30614-i0qc0q.30614.4016.csv => bqtest2-xxxxx:mydataset.LOAD_TEMP_e58cad5e_7a7b_41bc_9194_ffe3e08d40e3_hello_embulk in us/eu

The variable @location_for_log is used in the logger only.

236:              raise Error, "failed to load #{path} to #{@destination_project}:#{@dataset}.#{table} in #{@location_for_log}, response:#{response}"
359:            Embulk.logger.info { "embulk-output-bigquery: Create dataset... #{@destination_project}:#{dataset} in #{@location_for_log}" }
375:            Embulk.logger.debug { "embulk-output-bigquery: insert_dataset(#{@project}, #{dataset}, #{@location_for_log}, #{body}, #{opts})" }
387:            raise Error, "failed to create dataset #{@destination_project}:#{dataset} in #{@location_for_log}, response:#{response}"
451:            Embulk.logger.debug { "embulk-output-bigquery: insert_table(#{@destination_project}, #{dataset}, #{@location_for_log}, #{body}, #{opts})" }
461:              "embulk-output-bigquery: insert_table(#{@destination_project}, #{dataset}, #{@location_for_log}, #{body}, #{opts}), response:#{response}"
463:            raise Error, "failed to create table #{@destination_project}:#{dataset}.#{table} in #{@location_for_log}, response:#{response}"

[joker1007]

@hiroyuki-sato
Thank you for your comment.

1. Does Primary locations (_response.job_reference.location ) mean it contains other places neither us nor eu ? (ex: asia-northeast1?) JobReference

Yes. For example a dataset location is asia-northeast1, insert_job can submit without location and returned response includes location field having "asia-northeast1".

2. This change keeps the current behavior except the log message. correct?

Yes. at least I don't intend it.

[hiroyuki-sato]

LGTM👍 Thanks!