Fixed some crashes in response strings source generator, reorganized more submodules into their folders

src/NadekoBot/Modules/Nsfw/_Common/Downloaders/GelbooruImageDownloader.cs

@@ -0,0 +1,35 @@
+#nullable disable
+using System.Text.Json;
+
+namespace NadekoBot.Modules.Nsfw.Common;
+
+public class GelbooruImageDownloader : ImageDownloader<DapiImageObject>
+{
+    public GelbooruImageDownloader(HttpClient http)
+        : base(Booru.Gelbooru, http)
+    {
+    }
+
+    public override async Task<List<DapiImageObject>> DownloadImagesAsync(
+        string[] tags,
+        int page,
+        bool isExplicit = false,
+        CancellationToken cancel = default)
+    {
+        var tagString = ImageDownloaderHelper.GetTagString(tags, isExplicit);
+        var uri = "http://gelbooru.com/index.php?page=dapi&s=post&json=1&q=index&limit=100"
+                  + $"&tags={tagString}&pid={page}";
+        using var req = new HttpRequestMessage(HttpMethod.Get, uri);
+        using var res = await _http.SendAsync(req, cancel);
+        res.EnsureSuccessStatusCode();
+        var resString = await res.Content.ReadAsStringAsync(cancel);
+        if (string.IsNullOrWhiteSpace(resString))
+            return new();
+
+        var images = JsonSerializer.Deserialize<List<DapiImageObject>>(resString, _serializerOptions);
+        if (images is null)
+            return new();
+
+        return images.Where(x => x.FileUrl is not null).ToList();
+    }
+}