allow empty clientsecret and fix clientid null in sample

[Erwinvandervalk]

What issue does this PR address?

• allow empty client secret
• fix issue with sample and clientid null

[Copilot]

Pull Request Overview

This PR enables using a null/empty client secret without throwing during token requests and adds a fallback when the client ID is missing in the sample.

• Tests are updated to expect a successful token even when ClientSecret is null.
• Validation and runtime checks for a null ClientSecret are removed.
• The Blazor sample now handles a missing ClientId by falling back to configuration or a hard-coded value.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
access-token-management/test/AccessTokenManagement.Tests/ClientTokenManagementTests.cs	Test now expects a token instead of an exception for empty secret
access-token-management/src/AccessTokenManagement/Internal/ClientCredentialsTokenClient.cs	Removed null check for ClientSecret before sending form data
access-token-management/src/AccessTokenManagement/ClientCredentialsClient.cs	Removed options validation error for null ClientSecret
access-token-management/samples/BlazorServer/Plumbing/OidcEvents.cs	Added fallback for missing ClientId and updated comments

Comments suppressed due to low confidence (2)

access-token-management/test/AccessTokenManagement.Tests/ClientTokenManagementTests.cs:68

• [nitpick] The test name indicates an exception is expected, but the behavior changed to return a token. Consider renaming this to something like Allow_empty_client_secret_returns_token for clarity.

    public async Task Missing_client_secret_throw_exception()

access-token-management/test/AccessTokenManagement.Tests/ClientTokenManagementTests.cs:82

• [nitpick] The identifier The.ClientId is unclear—either use ClientId.Parse("test") inline or define a well-named constant to improve readability.

                client.ClientId = The.ClientId;