feat: allow post authors to pin comments

backend/src/main/java/com/openisle/controller/AdminCommentController.java

@@ -0,0 +1,29 @@
+package com.openisle.controller;
+
+import com.openisle.dto.CommentDto;
+import com.openisle.mapper.CommentMapper;
+import com.openisle.service.CommentService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.bind.annotation.*;
+
+/**
+ * Endpoints for administrators to manage comments.
+ */
+@RestController
+@RequestMapping("/api/admin/comments")
+@RequiredArgsConstructor
+public class AdminCommentController {
+    private final CommentService commentService;
+    private final CommentMapper commentMapper;
+
+    @PostMapping("/{id}/pin")
+    public CommentDto pin(@PathVariable Long id, Authentication auth) {
+        return commentMapper.toDto(commentService.pinComment(auth.getName(), id));
+    }
+
+    @PostMapping("/{id}/unpin")
+    public CommentDto unpin(@PathVariable Long id, Authentication auth) {
+        return commentMapper.toDto(commentService.unpinComment(auth.getName(), id));
+    }
+}