[dotnet] Fix Virtual Authenticator removal, annotate NRT

[RenderMichael]

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Description

This fixes a bug where the RemoveVirtualAuthenticator method does not use its parameter, and instead uses the cached authenticator ID value. This blocks scenarios where multiple VA's are running at once.

Additionally, Nullable Reference Type support (as well as improved null checks) have been added. Exceptional scenarios have been documented.

Motivation and Context

Contributes to #14640

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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PR Type

Bug fix, Enhancement, Tests

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Description

• Fixed a bug in RemoveVirtualAuthenticator method to correctly use its parameter, allowing multiple virtual authenticators to be managed.
• Enhanced the Credential class and other related classes with nullable reference type support and added null checks.
• Improved documentation across several classes, detailing exceptions and method behaviors.
• Added new tests to verify handling of multiple virtual authenticators and invalid arguments.

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Changes walkthrough 📝

	Relevant files
Enhancement	Credential.cs Enhance Credential class with null checks and NRT support dotnet/src/webdriver/VirtualAuth/Credential.cs Enabled nullable reference types. Added null checks and exceptions for constructor parameters. Updated property implementations to use expression-bodied members. Improved method documentation with exception details. +37/-49
Documentation	IHasVirtualAuthenticator.cs Add exception handling documentation to interface methods dotnet/src/webdriver/VirtualAuth/IHasVirtualAuthenticator.cs Enabled nullable reference types. Added exception documentation for methods. +14/-0    VirtualAuthenticatorOptions.cs Enhance VirtualAuthenticatorOptions with detailed documentation dotnet/src/webdriver/VirtualAuth/VirtualAuthenticatorOptions.cs Enabled nullable reference types. Improved method documentation with exception details. Added remarks and completion list tags for methods. +31/-25
Bug fix	WebDriver.cs Fix and enhance WebDriver virtual authenticator methods    dotnet/src/webdriver/WebDriver.cs Enabled nullable reference types. Added null checks and exceptions for method parameters. Improved method documentation with exception details. Fixed bug in RemoveVirtualAuthenticator method to use parameter. +63/-16
Tests	VirtualAuthenticatorTest.cs Add tests for virtual authenticator scenarios and error handling dotnet/test/common/VirtualAuthn/VirtualAuthenticatorTest.cs Added tests for multiple virtual authenticators. Added tests for invalid argument handling. +55/-1

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PR Reviewer Guide 🔍

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⏱️ Estimated effort to review: 3 🔵🔵🔵⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Possible Bug The AddVirtualAuthenticator method assigns the id before returning it, which could lead to race conditions if multiple authenticators are added concurrently Code Smell The userHandle field is cloned in the UserHandle property but not in the constructor, which could lead to inconsistent defensive copying Performance Issue The GetCredentials method creates a new list with known capacity but still uses Add() instead of setting indices directly

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Fix incorrect authenticator ID being used in removal request The RemoveVirtualAuthenticator method is using the wrong authenticator ID in the parameters dictionary. It should use the provided authenticatorId parameter instead of this.AuthenticatorId. dotnet/src/webdriver/WebDriver.cs [1066-1077] public void RemoveVirtualAuthenticator(string authenticatorId) { Dictionary<string, object> parameters = new Dictionary<string, object>(); - parameters.Add("authenticatorId", this.AuthenticatorId); + parameters.Add("authenticatorId", authenticatorId); this.Execute(DriverCommand.RemoveVirtualAuthenticator, parameters); this.AuthenticatorId = null; } Apply this suggestion Suggestion importance[1-10]: 10 Why: Critical bug fix - the method was using the cached authenticator ID instead of the provided parameter, which would cause removal of the wrong authenticator and potential security issues.	10
	Add response type validation to prevent runtime casting exceptions The GetCredentials method should validate the response value type before casting to avoid potential runtime exceptions. dotnet/src/webdriver/WebDriver.cs [1117-1118] -object[] commandResponse = (object[])this.Execute(driverCommandToExecute: DriverCommand.GetCredentials, parameters).Value; +Response getCredentialsResponse = this.Execute(driverCommandToExecute: DriverCommand.GetCredentials, parameters); +if (getCredentialsResponse.Value is not object?[] credentialsList) +{ + throw new WebDriverException($"Get credentials call succeeded, but the response was not a list of credentials: {getCredentialsResponse.Value}"); +} Apply this suggestion Suggestion importance[1-10]: 8 Why: Important defensive programming improvement that prevents potential runtime exceptions by validating the response type before casting, making the code more robust and maintainable.	8

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[nvborisenko]

Ci is failing, I guess because of some invisible character.

[RenderMichael]

@nvborisenko fixed🤦

[nvborisenko]

/automerge, thanks Michael for contribution.