Persona separation is tested, the API is smoke-checked on deploy, OAuth rows are pruned

- PersonaSeparationTests: two personas of one login follow the same
  account and post; nothing the API maps for one contains the other's id,
  username or the root id.
- tools/smoke/mastodon-api.sh checks what a client meets first (instance
  v1/v2, discovery, app registration, client credentials, an app token
  refused by a user endpoint, the public timeline, revocation) and, given
  a persona token, verify_credentials, home and notifications. deploy.yml
  runs it after every deploy.
- OAuthPruner removes invalid tokens and authorizations older than two
  weeks, every six hours.
- The consent page no longer sets form-action, which browsers apply to the
  redirect back to the client after the form is posted.

CLAUDE.md gains the Mastodon API layout and invariants.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Api/Mastodon/Auth/OAuthPruner.cs

@@ -0,0 +1,44 @@
+using OpenIddict.Abstractions;
+
+namespace PrivaPub.Api.Mastodon.Auth
+{
+	public class OAuthPruner : BackgroundService
+	{
+		static readonly TimeSpan Interval = TimeSpan.FromHours(6);
+		static readonly TimeSpan Threshold = TimeSpan.FromDays(14);
+
+		readonly IServiceProvider _services;
+		readonly ILogger<OAuthPruner> _logger;
+
+		public OAuthPruner(IServiceProvider services, ILogger<OAuthPruner> logger)
+		{
+			_services = services;
+			_logger = logger;
+		}
+
+		protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+		{
+			while (!stoppingToken.IsCancellationRequested)
+			{
+				try
+				{
+					await Task.Delay(Interval, stoppingToken);
+					using var scope = _services.CreateScope();
+					var threshold = DateTimeOffset.UtcNow - Threshold;
+					var tokens = await scope.ServiceProvider.GetRequiredService<IOpenIddictTokenManager>().PruneAsync(threshold, stoppingToken);
+					var authorizations = await scope.ServiceProvider.GetRequiredService<IOpenIddictAuthorizationManager>().PruneAsync(threshold, stoppingToken);
+					if (tokens + authorizations > 0)
+						_logger.LogInformation("{Service} removed {Tokens} tokens and {Authorizations} authorizations", nameof(OAuthPruner), tokens, authorizations);
+				}
+				catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+				{
+					return;
+				}
+				catch (Exception ex)
+				{
+					_logger.LogWarning(ex, "{Service} pass failed", nameof(OAuthPruner));
+				}
+			}
+		}
+	}
+}

PrivaPub/Api/Mastodon/Auth/OAuthSetup.cs

@@ -26,6 +26,7 @@ namespace PrivaPub.Api.Mastodon.Auth
 		public static IServiceCollection PrivaPubOAuth(this IServiceCollection services, IWebHostEnvironment environment)
 		{
 			services.AddSingleton<IMongoDatabase>(_ => DB.Default.Database());
+			services.AddHostedService<OAuthPruner>();
 
 			services.AddAuthentication()
 				.AddCookie(LoginScheme, options =>