Fix newsletter confirmation: handle already-confirmed idempotently and protect confirmed subscriber preferences

[Copilot]

Confirmation links showed "Invalid or expired" after a valid click due to Blazor SSR pre-rendering the page (calling the API) and then the interactive client calling it again on a fresh component instance. Also, anyone could silently overwrite a confirmed subscriber's preferences by POSTing to /api/newsletter/subscribe with their email.

Changes

ConfirmSubscriptionResult enum (new)

• Tri-state result: Confirmed / AlreadyConfirmed / InvalidToken
• Replaces the bool return across INewsletterSubscriberRepository, INewsletterService, and the endpoint

Repository — ConfirmSubscriberAsync

• When UPDATE … WHERE is_confirmed = FALSE matches 0 rows, does a follow-up SELECT to distinguish AlreadyConfirmed from InvalidToken (subscriber not found / unsubscribed)

API endpoint — ConfirmAsync

• Confirmed and AlreadyConfirmed both return HTTP 200 with distinct messages; InvalidToken returns 400

return result switch
{
    ConfirmSubscriptionResult.Confirmed       => Results.Ok(new { message = "Your subscription is confirmed." }),
    ConfirmSubscriptionResult.AlreadyConfirmed => Results.Ok(new { message = "Your subscription has already been confirmed." }),
    _                                          => Results.BadRequest("Invalid or expired confirmation link.")
};

Repository — UpsertSubscriberAsync

• SQL DO UPDATE SET now uses CASE WHEN is_confirmed = FALSE guards so a re-subscribe request never overwrites an already-confirmed subscriber's display_name or preferences

Web client / Blazor page

• ConfirmNewsletterAsync returns Task<string> (the message from the response body) instead of Task
• NewsletterConfirm.razor displays the API-provided message rather than a hardcoded string

[Copilot]

Pull request overview

This PR fixes newsletter confirmation being non-idempotent (breaking in Blazor SSR prerender + hydration) and closes a security gap where re-subscribing could overwrite preferences for already-confirmed subscribers.

Changes:

• Introduces ConfirmSubscriptionResult (Confirmed / AlreadyConfirmed / InvalidToken) and propagates it through Core interfaces, Infrastructure service/repository, and API confirm endpoint.
• Makes confirmation idempotent at the repository level by distinguishing “already confirmed” vs “invalid token/not found”.
• Prevents overwriting display_name / preferences for confirmed subscribers on UpsertSubscriberAsync, and updates Web/API tests accordingly.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/TechHub.Infrastructure.Tests/Repositories/NewsletterSubscriberRepositoryTests.cs	Adds coverage for new confirm result states and confirmed-subscriber no-overwrite behavior.
tests/TechHub.Api.Tests/Endpoints/NewsletterEndpointsTests.cs	Adds integration tests for confirm responses/messages and preference overwrite protection via subscribe endpoint.
src/TechHub.Web/Services/TechHubApiClient.cs	Updates confirm call to return the API-provided message.
src/TechHub.Web/Services/ITechHubApiClient.cs	Updates interface to return the confirmation message string.
src/TechHub.Web/Components/Pages/NewsletterConfirm.razor	Displays API-provided confirmation message instead of a hardcoded one.
src/TechHub.Infrastructure/Services/Newsletter/NewsletterService.cs	Changes confirm method to return ConfirmSubscriptionResult and propagates invalid token/secret cases.
src/TechHub.Infrastructure/Repositories/NewsletterSubscriberRepository.cs	Makes confirm idempotent and guards UPSERT updates so confirmed subscribers aren’t overwritten.
src/TechHub.Core/Models/ConfirmSubscriptionResult.cs	Adds new enum modeling the tri-state confirmation result.
src/TechHub.Core/Interfaces/INewsletterSubscriberRepository.cs	Updates confirm contract to return ConfirmSubscriptionResult.
src/TechHub.Core/Interfaces/INewsletterService.cs	Updates confirm contract to return ConfirmSubscriptionResult.
src/TechHub.Api/Endpoints/NewsletterEndpoints.cs	Returns 200 for both Confirmed/AlreadyConfirmed with distinct messages; 400 for InvalidToken.

[rvanmaanen]

@copilot can you fix this?

[Copilot]

Done in the latest commit. NewsletterConfirm.razor now uses PersistentComponentState: during SSR prerender the result (_message + _success) is persisted to the HTML payload, and on interactive hydration the new component instance restores from that state in OnInitializedAsync instead of calling the API a second time. The old _handled guard and OnParametersSetAsync are replaced with the standard OnInitializedAsync + IDisposable pattern used by other pages in the project.

[github-actions]

⏰ PR Preview Environment — Nightly Teardown

The preview environment was automatically torn down as part of the nightly cleanup (23:00 Brussels time).

To resume testing:

• Push a new commit to this branch to automatically re-deploy (full CI + new images), or
• Trigger the Redeploy PR Environment workflow manually to redeploy using the last-built image (no new commit needed).

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.