feat: add macro to apply tags to source columns in on-run-end hook

[bsuryachandra]

resolves #15

This is a:

• documentation update
• bug fix with no breaking changes
• new functionality
• a breaking change

All pull requests from community contributors should target the main branch (default).

Description & motivation

This PR introduces a new macro, apply_source_column_tags, which applies tags to the columns of all source tables. The macro can be used in the on-run-end hook to automate tagging source columns. It operates similarly to the existing apply_column_tags macro but is specifically designed for source tables.

The purpose of this change is to provide a streamlined method for applying tags to source columns, improving metadata management and enhancing data traceability. By tagging both models and source columns uniformly, it becomes easier to manage important or sensitive data within the data pipeline.

Checklist

• This code is associated with an Issue which has been triaged and accepted for development
• I have verified that these changes work locally on the following warehouses (Note: it's okay if you do not have access to all warehouses, this helps us understand what has been covered)
  • Snowflake
• I have updated the README.md (if applicable)
• I have added tests & descriptions to my models (and macros if applicable)

[il-dat]

Thanks @bsuryachandra looks very great PR!

I have some comments from the general view, could you help to give it a look? I will try to dive into testing this PR in they next days, will approve it if all looks good 🏃‍♂️

[thu-IL]

Can you please also modify the model verify_if_masking_policies_applied_correctly to check if tags are applied correctly to the source columns as intended?