Follow requests nobody answers are sent again

A Follow was resent only when the persona followed again. Lemmy 1.0
sends nothing it queued for a server before it started sending there, so
the Accept of a community follow made on first contact was lost for good:
the village's persona stayed "requested" a day while Lemmy listed her as a
follower, and every post the community announced was refused as not
followed. A request still unanswered is now sent again, the same activity,
after 15 minutes, an hour, 6 hours, a day, two and four days
(FollowResender, every 15 minutes); a server that holds the follow answers
the copy.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Domain/Social/FollowResender.cs

@@ -0,0 +1,27 @@
+namespace PrivaPub.Domain.Social
+{
+	// sends again, now and then, the follow requests still unanswered (FollowService.ResendPending)
+	public sealed class FollowResender(IServiceScopeFactory scopes, ILogger<FollowResender> logger) : BackgroundService
+	{
+		static readonly TimeSpan Every = TimeSpan.FromMinutes(15);
+
+		protected override async Task ExecuteAsync(CancellationToken token)
+		{
+			using var timer = new PeriodicTimer(Every);
+			while (await timer.WaitForNextTickAsync(token))
+			{
+				try
+				{
+					using var scope = scopes.CreateScope();
+					var sent = await scope.ServiceProvider.GetRequiredService<IFollowService>().ResendPending(DateTime.UtcNow, token);
+					if (sent > 0)
+						logger.LogInformation("Sent {Count} unanswered follow requests again", sent);
+				}
+				catch (Exception ex) when (ex is not OperationCanceledException)
+				{
+					logger.LogWarning(ex, "Unanswered follow requests could not be sent again");
+				}
+			}
+		}
+	}
+}