refactor(hiTeachSideMenu): use the Constant class to retrieve strings instead of literals

TEAMModelOS/Services/ContentService.cs

@@ -61,7 +61,7 @@ namespace TEAMModelOS.Services
                     subjectId = subjectId.ToList(),
                     gradeId = gradeId.ToList(),
                 };
-                await _writeFileRecord("School", id, bloblog);
+                await _writeFileRecord(Constant.School, id, bloblog);
         }
 
         public async Task UploadToPrivate(IFormFile file, string id)
@@ -92,7 +92,7 @@ namespace TEAMModelOS.Services
                 subjectId = new List<string> {},
                 gradeId = new List<string> {},
             };
-            await _writeFileRecord("Teacher", id, bloblog);
+            await _writeFileRecord(Constant.Teacher, id, bloblog);
         }
 
         private string _getFileType(string extension)