feat(backend): initial data export support

obviously it's missing things that haven't been added yet

Foxnouns.Backend/Controllers/ExportsController.cs

@@ -0,0 +1,74 @@
+using Coravel.Queuing.Interfaces;
+using Foxnouns.Backend.Database;
+using Foxnouns.Backend.Database.Models;
+using Foxnouns.Backend.Jobs;
+using Foxnouns.Backend.Middleware;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using NodaTime;
+
+namespace Foxnouns.Backend.Controllers;
+
+[Route("/api/internal/data-exports")]
+[Authorize("identify")]
+public class ExportsController(
+    ILogger logger,
+    Config config,
+    IClock clock,
+    DatabaseContext db,
+    IQueue queue
+) : ApiControllerBase
+{
+    private static readonly Duration MinimumTimeBetween = Duration.FromDays(1);
+    private readonly ILogger _logger = logger.ForContext<ExportsController>();
+
+    [HttpGet]
+    public async Task<IActionResult> GetDataExportsAsync()
+    {
+        var export = await db
+            .DataExports.Where(d => d.UserId == CurrentUser!.Id)
+            .OrderByDescending(d => d.Id)
+            .FirstOrDefaultAsync();
+        if (export == null)
+            return Ok(new DataExportResponse(null, null));
+
+        return Ok(
+            new DataExportResponse(
+                ExportUrl(CurrentUser!.Id, export.Filename),
+                export.Id.Time + DataExport.Expiration
+            )
+        );
+    }
+
+    private string ExportUrl(Snowflake userId, string filename) =>
+        $"{config.MediaBaseUrl}/data-exports/{userId}/{filename}.zip";
+
+    private record DataExportResponse(string? Url, Instant? ExpiresAt);
+
+    [HttpPost]
+    public async Task<IActionResult> QueueDataExportAsync()
+    {
+        var snowflakeToCheck = Snowflake.FromInstant(
+            clock.GetCurrentInstant() - MinimumTimeBetween
+        );
+        _logger.Debug(
+            "Checking if user {UserId} has data exports newer than {Snowflake}",
+            CurrentUser!.Id,
+            snowflakeToCheck
+        );
+        if (
+            await db.DataExports.AnyAsync(d =>
+                d.UserId == CurrentUser.Id && d.Id > snowflakeToCheck
+            )
+        )
+        {
+            throw new ApiError.BadRequest("You can't request a new data export so soon.");
+        }
+
+        queue.QueueInvocableWithPayload<CreateDataExportInvocable, CreateDataExportPayload>(
+            new CreateDataExportPayload(CurrentUser.Id)
+        );
+
+        return NoContent();
+    }
+}