added get episode by number endpoint

server/Persistence/Repositories/EpisodeRepository.cs

@@ -32,5 +32,18 @@ namespace server.Persistence.Repositories
                 throw;
             }
         }
+
+        public async Task<Episode> GetEpisodeByNumberAsync(int number)
+        {
+            try
+            {
+                return await _context.Episodes.Find(episode => episode.NumberInSeries == number).SingleOrDefaultAsync();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+                throw;
+            }
+        }
     }
 }

server/Persistence/Repositories/IEpisodeRepository.cs

@@ -10,5 +10,6 @@ namespace server.Persistence.Repositories
     public interface IEpisodeRepository
     {
         Task<List<Episode>> GetEpisodesAsync(EpisodeFilter filter);
+        Task<Episode> GetEpisodeByNumberAsync(int number);
     }
 }