auto fallback when loading settings from env

[xiangyan99]

Invalid values for the AZURE_LOG_LEVEL, AZURE_TRACING_ENABLED, and AZURE_SDK_TRACING_IMPLEMENTATION environment variables no longer raise errors.

Description

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• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR changes azure-core settings parsing so invalid environment variable values no longer raise exceptions; instead they fall back to defaults and emit warnings.

Changes:

• Added warning-and-fallback behavior for invalid AZURE_LOG_LEVEL, AZURE_TRACING_ENABLED, and AZURE_SDK_TRACING_IMPLEMENTATION values.
• Added VERBOSE as an alias for DEBUG for AZURE_LOG_LEVEL.
• Updated docs and tests to reflect the new fallback behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
sdk/core/azure-core/azure/core/settings.py	Implements warning logs + fallback defaults; adds VERBOSE alias and updates docstrings.
sdk/core/azure-core/tests/test_settings.py	Updates tests to expect fallback return values; adds VERBOSE alias coverage.
sdk/core/azure-core/ENVIRONMENT_VARIABLES.md	Documents fallback behavior and VERBOSE alias.
sdk/core/azure-core/CLIENT_LIBRARY_DEVELOPER.md	Updates env var table to mention fallback behavior and VERBOSE.
sdk/core/azure-core/CHANGELOG.md	Notes behavior change (no error on invalid env vars) and the new VERBOSE alias.

[pvaneck]

Seems reasonable and LGTM.