fix uploading non string values

src/main/java/cc/fascinated/backend/controller/PasteController.java

@@ -3,6 +3,7 @@ package cc.fascinated.backend.controller;
 import cc.fascinated.backend.model.Paste;
 import cc.fascinated.backend.service.PasteService;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
@@ -26,7 +27,7 @@ public class PasteController {
         ));
     }
 
-    @PostMapping(value = "/upload")
+    @PostMapping(value = "/upload", consumes = MediaType.TEXT_PLAIN_VALUE)
     public ResponseEntity<?> uploadPaste(@RequestBody String content) {
         String id = pasteService.createPaste(content);
         return ResponseEntity.ok(Map.of("id", id));