[docs] Fix outdated API references in management tests documentation

[Ali Satwat Khan (alisatwat3)]

Description

Fixes #48400.

Updates doc/dev/mgmt/tests.md to match the current credential and management-test implementation:

• Use client_secret and tenant_id with ClientSecretCredential.
• Replace the obsolete mgmt_settings_real.py workflow with the environment-variable-based live-test setup, including AZURE_SUBSCRIPTION_ID.
• Clarify that AzureMgmtRecordedTestCase uses fake credentials during playback and environment-based credentials in live mode.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes. Not applicable; documentation-only correction.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message.

Testing Guidelines

• Pull request includes test coverage for the included changes. Not applicable; documentation-only change validated with git diff --check and cross-checked against the current test framework implementation.

[github-actions]

Thank you for your contribution Ali Satwat Khan (@alisatwat3)! We will review the pull request and get back to you soon.

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[Copilot]

Pull request overview

Updates management testing documentation to use current credential parameter, helper, and base-class names.

Changes:

• Corrects ClientSecretCredential keyword arguments.
• Updates credential helper and test base-class references.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Suppressed comments (1)

doc/dev/mgmt/tests.md:172

• create_mgmt_client() does not perform checks that verify the client was created successfully; it only constructs the client, applies playback configuration, and returns it (azure_recorded_testcase.py:100-122). This wording can incorrectly imply failures will be detected before the first service operation, so remove the validation claim.

3. The `create_mgmt_client()` helper method of `AzureMgmtRecordedTestCase` creates a client object using fake credentials during playback or credentials from environment variables in live mode, with some checks to make sure it's created successfully and cause the unit test to fail if not. You should use it for any clients you create.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Suppressed comments (1)

doc/dev/mgmt/tests.md:102

• These two commands are not copyable as written: both CMD and POSIX shells interpret the unquoted </> placeholder characters as redirection operators rather than part of the value. Quote the assignment so readers can run the documented commands and then replace the placeholder safely.

set AZURE_SUBSCRIPTION_ID=<value>           # Windows CMD
export AZURE_SUBSCRIPTION_ID=<value>        # Linux shell only