Fix SQL container throughput update to preserve existing throughput buckets

[Achint-Agrawal]

Fixes a bug where updating SQL container throughput would reset existing throughput buckets to None when the --throughput-buckets parameter was not explicitly provided. The fix preserves existing throughput buckets when the parameter is omitted, only removing them when explicitly set to an empty array.
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Related command

az cosmosdb sql container throughput update

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[azure-client-tools-bot-prd]

️✔️Azure CLI Extensions Breaking Change Test

️✔️Non Breaking Changes

[azure-client-tools-bot-prd]

Hi @Achint-Agrawal,
Please write the description of changes which can be perceived by customers into HISTORY.rst.
If you want to release a new extension version, please update the version in setup.py as well.

[yonzhan]

Thank you for your contribution! We will review the pull request and get back to you soon.

[github-actions]

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[Copilot]

Pull Request Overview

This PR fixes a bug in the CosmosDB SQL container throughput update functionality where existing throughput buckets were being unintentionally reset to None when the --throughput-buckets parameter was not explicitly provided. The fix preserves existing throughput buckets when the parameter is omitted and only removes them when explicitly set to an empty array.

Key changes:

• Added logic to preserve existing throughput buckets when the parameter is not provided
• Enhanced test coverage to verify both bucket preservation and explicit bucket removal scenarios

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 2 comments.

File	Description
custom.py	Added logic to retrieve and preserve existing throughput buckets when throughput_buckets parameter is None
test_cosmosdb_sql_throughput_bucketing_scenario.py	Added comprehensive test cases to verify bucket preservation and explicit removal behavior

[github-actions]

• For more info about extension versioning, please refer to Extension version schema

[azclibot]

[Release] Update index.json for extension [ cosmosdb-preview-1.6.1 ] : https://dev.azure.com/msazure/One/_build/results?buildId=132367107&view=results