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This PR covers various improvements to the [recently
merged](https://github.com/snowflakedb/managed-pull/7) Polaris
CLI. Changes here include:
* Added the `namespaces` command for creating, listing, and dropping
namespaces with the CLI
* Refactored error handling to reduce the proliferation of string
literals
* Added support for the `FILE` storage type
* Added end-to-end regression tests for the CLI
* Various usability and bug fixes
* Support for the `CLIENT_ID` and `CLIENT_SECRET` environment variables
* CLI documentation
## Pre-review checklist
- [ ] I attest that this change meets the bar for low risk without
security requirements as defined in the [Accelerated Risk Assessment
Criteria](https://developer-handbook.m1.us-west-2.aws.app.snowflake.com/docs/reference/security-review/accelerated-risk-assessment/#eligibility)
and I have taken the [Risk Assessment Training in
Workday](https://wd5.myworkday.com/snowflake/learning/course/6c613806284a1001f111fedf3e4e0000).
- Checking this checkbox is mandatory if using the [Accelerated Risk
Assessment](https://developer-handbook.m1.us-west-2.aws.app.snowflake.com/docs/reference/security-review/accelerated-risk-assessment/)
to risk assess the changes in this Pull Request.
- If this change does not meet the bar for low risk without security
requirements (as confirmed by the peer reviewers of this pull request)
then a [formal Risk
Assessment](https://developer-handbook.m1.us-west-2.aws.app.snowflake.com/docs/reference/security-review/risk-assessment/)
must be completed. Please note that a formal Risk Assessment will
require you to spend extra time performing a security review for this
change. Please account for this extra time earlier rather than later to
avoid unnecessary delays in the release process.
- [ ] This change has code coverage for the new code added