DBT set column metadata using macros

I'm trying to set my column metadata in sql using macros instead of in yml, but can't figure out if this is possible.

I'm currently successfully setting policy_tags in the yml, eg test.yml:

version: 2

models:
- name: test
  columns:
    - name: a
      policy_tags: ["MY_TAG"]

However, I'd like to do the same thing in SQL, with something like:

{# FAKE CODE, DOESN'T WORK %#}
{{ config.set('columns', [{ name: "a", policy_tags: ["MY_TAG"] }]) }}

I'm dynamically generating a variable number of columns in the sql using macros, so this would let me also dynamically tag all those columns. Any suggestions appreciated!

Turned out I was able to do this in a post_hook by calling persist_docs directly:

# my_model.sql
{{ config({'post-hook': "{{ write_policy_tags() }}"}) }}

## write_policy_tags.sql
{% macro write_policy_tags() %}
  {% set columns = {
    "col1": { "policy_tags": ["{{ col1tag }}"] },
    "col2": { "policy_tags": ["{{ col2tag }}"] }
  } %}
  {% do persist_docs(this, { "columns": columns }) %}
{% endmacro %}

Within the macro, I was then able to call run_query and use the results to dynamically generate the columns variable to pass to persist_docs, which achieved my original goal of dynamic policy_tags.