Add DJ status check endpoint to music routes

Introduced `/music/{guildId}/dj/{userId}` endpoint to verify if a user has DJ permissions in a specific guild. Added `DjStatusResponse` DTO, integrated the logic into `MusicManager`, and provided OpenAPI documentation for the new route.

src/main/java/me/bobert/netneutrality/http/server/MusicRoutes.java

@@ -18,6 +18,7 @@ import io.javalin.openapi.OpenApiParam;
 import io.javalin.openapi.OpenApiRequestBody;
 import io.javalin.openapi.OpenApiResponse;
 import me.bobert.netneutrality.http.server.dto.CommandResultResponse;
+import me.bobert.netneutrality.http.server.dto.DjStatusResponse;
 import me.bobert.netneutrality.http.server.dto.ErrorResponse;
 import me.bobert.netneutrality.http.server.dto.MusicSourceResponse;
 import me.bobert.netneutrality.http.server.dto.MusicStatusResponse;
@@ -38,6 +39,7 @@ import me.bobert.netneutrality.music.PlayOutcome;
 import me.bobert.netneutrality.music.QueueActionResult;
 import me.bobert.netneutrality.music.SourceFinder;
 import me.bobert.netneutrality.music.TrackInfo;
+import me.bobert.netneutrality.utils.MusicUtils;
 import net.dv8tion.jda.api.JDA;
 import net.dv8tion.jda.api.entities.Guild;
 import net.dv8tion.jda.api.entities.Member;
@@ -73,6 +75,7 @@ public final class MusicRoutes {
         routes.put("/music/{guildId}/volume", ctx -> volume(jdaSupplier, musicService, ctx));
         routes.put("/music/{guildId}/seek", ctx -> seek(jdaSupplier, musicService, ctx));
         routes.post("/music/{guildId}/vote-skip/{userId}", ctx -> voteSkip(jdaSupplier, musicService, ctx));
+        routes.get("/music/{guildId}/dj/{userId}", ctx -> dj(jdaSupplier, musicService, ctx));
         routes.post("/music/{guildId}/queue", ctx -> play(jdaSupplier, musicService, ctx));
         routes.patch("/music/{guildId}/queue/reorder", ctx -> reorder(jdaSupplier, musicService, ctx));
         routes.post("/music/{guildId}/search", ctx -> search(jdaSupplier, musicService, ctx));
@@ -334,6 +337,33 @@ public final class MusicRoutes {
         );
     }
 
+    @OpenApi(
+        path = "/music/{guildId}/dj/{userId}",
+        methods = HttpMethod.GET,
+        summary = "Check whether a guild member is currently allowed to control music playback as the DJ",
+        tags = {"Music"},
+        pathParams = {
+            @OpenApiParam(name = "guildId", description = "The Discord guild id"),
+            @OpenApiParam(name = "userId", description = "The Discord user id to check")
+        },
+        responses = {
+            @OpenApiResponse(status = "200", content = @OpenApiContent(from = DjStatusResponse.class)),
+            @OpenApiResponse(status = "404", content = @OpenApiContent(from = ErrorResponse.class))
+        }
+    )
+    private static void dj(Supplier<JDA> jdaSupplier, MusicService musicService, Context ctx) {
+        Guild guild = GuildRoutes.guild(jdaSupplier, ctx);
+        MusicManager manager = musicService.get(guild);
+        String userId = ctx.pathParam("userId");
+
+        CacheOrFetch.<Member>resolve(
+            ctx,
+            () -> guild.getMemberById(userId),
+            () -> guild.retrieveMemberById(userId),
+            member -> new DjStatusResponse(userId, MusicUtils.isUserDj(member, manager))
+        );
+    }
+
     @OpenApi(
         path = "/music/{guildId}/queue",
         methods = HttpMethod.POST,

src/main/java/me/bobert/netneutrality/http/server/dto/DjStatusResponse.java

@@ -0,0 +1,16 @@
+package me.bobert.netneutrality.http.server.dto;
+
+/*
+ * Copyright (c) anthorob
+ *
+ * https://discord.gg/qUa6zNFZsd
+ */
+
+/**
+ * OpenAPI schema for the {@code /music/{guildId}/dj/{userId}} response.
+ */
+public record DjStatusResponse(
+    String userId,
+    boolean isDj
+) {
+}