chore: switch identifyUser to return InvalidUser error in callback

[jonathannorris]

• Remove throws from identifyUser, and return ClientError.InvalidUser in error callback like the config errors

[Copilot]

Pull Request Overview

This PR removes the throwing behavior from identifyUser and switches to reporting ClientError.InvalidUser via the callback, aligning it with how other errors are handled.

• Updated the synchronous identifyUser to call the callback with .InvalidUser instead of throwing.
• Refactored the async wrapper to use the callback-based API in a throwing continuation.
• Added new unit tests to verify error behavior for invalid users in both callback and async forms.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
DevCycle/DevCycleClient.swift	Changed identifyUser to non-throwing, invoke error callback on invalid input, and refactored async
DevCycleTests/Models/DevCycleClientTests.swift	Added tests for identifyUser errors when given an empty user ID in both callback and async cases

Comments suppressed due to low confidence (2)

DevCycle/DevCycleClient.swift:426

• The method signature was updated to remove throws but any existing doc comments or API documentation should also be updated to reflect this change and indicate that errors are now delivered via the callback.

    public func identifyUser(user: DevCycleUser, callback: IdentifyCompletedHandler? = nil) {

DevCycleTests/Models/DevCycleClientTests.swift:804

• The async test creates an XCTestExpectation but never waits for it, which may cause the test to complete before assertions are executed. Either remove the expectation and assert directly in the async context or add a wait(for:timeout:) (or await fulfillment(of:timeout:)) to ensure the expectation is fulfilled.

    func testAsyncIdentifyUserWithInvalidUserCallsCallbackWithError() async throws {

[jonathannorris]

ugh @jsalaber now that change means this is an issue:

Which is probably a lot of folks are using identifyUser without setting a callback :(