Add granularity to Permifrost write permissions

Currently granting write permissions via Permifrost on an object, will grant all the write permissions a role can possibly have on that object, as illustrated on the spec_file section of the readme.

This issue is meant as a spike discussing if it would be possible and in scope to add granularity to the granted permissions.

Some context for this request:

For data observability purposes, we will need a data observability role that has monitoring permissions on specific objects.

Currently, we can use Permifrost and grant write permissions, but that would provide extended write permissions, when what we need is just a subset of those.

Examples:

For databases, we would only need to grant usage & monitor to this role. Granting write permissions on database via Permifrost grants usage, monitor and create schema (which we do not need to grant).

For tables, we would only need to provide select & references permissions. Granting write permissions on table via Permifrost grants references and select, insert, update, delete, truncate.

Proposed changes

Ideally, these permissions could be grouped under a monitoring term and granted via an additional Permifrost permission called monitor. This is how granting read and monitor permissions to the prod database for the testing_permifrost_role role would look like:

 - testing_permifrost_role:
      warehouses:
          - data_observability_wh
      privileges:
         databases:
             read:
                - prod
             monitor: 
                - prod 

And this would be the new specification for Permifrost permissions mapped to Snowflake grants:

Objects	Permifrost permissions	Snowflake grants
Databases	read	usage
	write	create schema
	monitor	monitor
Schemas	read	usage
	write	create table, create view, create stage, create file format, create sequence, create function, create pipe
	monitor	monitor
Table	read	select
	write	insert, update, delete, truncate
	monitor	references

Who will this benefit?

The feature would benefit anyone who would like to have more granularity via Permifrost.

Are you interested in contributing this feature?

Yes