Remove experimental flag requirement from IAuthenticationOperation

[Copilot]

Changes proposed in this request

Removed experimental feature gate from IAuthenticationOperation and WithAuthenticationExtension. Developers can now use custom authentication operations without calling .WithExperimentalFeatures(true).

Two validations removed:

• WithAuthenticationOperation in AbstractAcquireTokenParameterBuilder.cs
• WithAdditionalCacheParameters in AbstractConfidentialClientAcquireTokenParameterBuilderExtension.cs

Updated tests in AuthenticationOperationTests.cs to remove .WithExperimentalFeatures(true) calls, demonstrating that the feature works without experimental flags.

Before:

var app = ConfidentialClientApplicationBuilder
    .Create(clientId)
    .WithClientSecret(secret)
    .WithExperimentalFeatures(true)  // Required
    .Build();

app.AcquireTokenForClient(scopes)
    .WithAuthenticationExtension(authExtension)
    .ExecuteAsync();

After:

var app = ConfidentialClientApplicationBuilder
    .Create(clientId)
    .WithClientSecret(secret)
    .Build();

app.AcquireTokenForClient(scopes)
    .WithAuthenticationExtension(authExtension)  // No experimental flag needed
    .ExecuteAsync();

Testing

Updated existing tests in AuthenticationOperationTests.cs:

• Should_UseCustomRequestHeaders_And_StoreAdditionalParameters
• Should_UseCustomRequestHeaders_And_StoreAdditionalParametersWithCaching
• Should_UseEmptyExtension_And_Parameters

All tests now run without .WithExperimentalFeatures(true) and pass successfully, proving that WithAuthenticationExtension works correctly for:

• AuthenticationOperation alone
• AdditionalCacheParameters alone
• Both combined

Performance impact

None. Removed validation calls, no new logic added.

Documentation

• All relevant documentation is updated.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature Request] Remove experimental flag from IAuthenticationOperation</issue_title>
<issue_description>### MSAL client type

Confidential

Problem statement

WithAuthenticationExtension should not be experimental, to avoid app developers having to set this flag.

Proposed solution

No response

Alternatives

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature Request] Remove experimental flag from IAuthenticationOperation #5698

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