Add apply_meta_as_tags macro

[jamesweakley]

This PR adds the apply_meta_as_tags as discussed here: dbt-labs/dbt-snowflake#104

Documentation is available in the readme, I opted for a yaml-driven approach.

Tested on a sample model with dbt 1.3.0.

[MartinGuindon]

Thank you for your contribution @jamesweakley. I will aim to merge this in the next few days!

[gmatsonANSYS]

@jamesweakley I tested your macro using the yaml driven approach and the macro only executes if a table and column tag are set on a model. Are you able to have tags created/set using only the column meta tags?

the log file shows " meta': {'database_tags': None}, 'transient': False}" and skips

[jamesweakley]

@gmatsonANSYS good pickup, I hadn't tried that scenario. Will take a look today

[jamesweakley]

@gmatsonANSYS it should now work even if you've only defined column tags

[gmatsonANSYS]

Thanks James, the updates worked as expected. The only tweaks I had to make were around the existing tag filters:

Converted the table and column name to upper - similar to the tag_name pipe - to return matches.
{%- set existing_tag_for_table = existing_tags|selectattr('0','equalto','TABLE')|selectattr('1','equalto',table_name|upper)|selectattr('2','equalto',column_name|upper)|selectattr('3','equalto',tag_name|upper)|list -%}

Updated to the fifth column index for the tag value comparison
{% if existing_tag_for_table|length > 0 and existing_tag_for_table[0][4]==desired_tag_value %}

[jamesweakley]

@gmatsonANSYS thanks for the code snippets, I've pushed some more changes and tested various matching/non-matching scenarios and it seems consistent now

[jamesweakley]

@gmatsonANSYS hopefully this all works in your test scenario now?

[gmatsonANSYS]

@jamesweakley runs smooth as silk. Thank you!

[MartinGuindon]

Awesome, if there are no further updates to this PR I'll be merging it shortly.

[MartinGuindon]

@jamesweakley The macro should be documented in macros.yml, and there's a typo in the README. Other than that, looks pretty good to me . Once fixed I'll merge and issue a new version.

[jamesweakley]

@MartinGuindon Thanks, I've pushed those changes now