Support description of columns and tables

[fagai]

trafficstars

related: #127 add tests. and fixed tests.

[kyoshidajp]

@fagai Thank you for adding tests.

[masaushi]

Hi, maintainers! Is this still under review? I need this feature, so I'm hoping this PR will be merged soon. Thank you maintainers for your time to maintain this project.

[hiroyuki-sato]

Hello, @fagai. I'm a new maintainer. Could you resolve conflict this PR? I'll review this PR. Or, I'll create another PR later.

[fagai]

@hiroyuki-sato I resolved the conflict.

[hiroyuki-sato]

@fagai Thank you for your work!.

Does this PR work as you expected? It seems the column is OK. But, the table doesn't set as you expected. What am I wrong?

out:
  type: bigquery
  mode: append
  # snip
  table: hello_embulk
  source_format: NEWLINE_DELIMITED_JSON
  column_options:
  - name: purchase
    description: hogehogehoge12345
  description: hogehoge

column: OK

table: NG??

[fagai]

@hiroyuki-sato Fixed an issue where config values ​​were not being read.

I don't have a deep understanding of ruby, so I may be wrong.

[hiroyuki-sato]

Thanks LGTM👍

@joker1007 Could you check this PR when you get a chance?

[hiroyuki-sato]

Thanks!