Added logic to stop duplicate shows from being announced using redis cache

AnimeAnnouncer/Cache/TMDBCache.cs

@@ -1,3 +1,4 @@
+using System.Security.Cryptography;
 using System.Text.Json;
 using StackExchange.Redis;
 using TMDbLib.Utilities.Converters;
@@ -20,7 +21,7 @@ public class TMDBCache
     {
         var db = redis.GetDatabase();
         String jsonItem = JsonSerializer.Serialize(item);
-        db.StringSetAsync(key, jsonItem, CacheExpiration);
+        await db.StringSetAsync(key, jsonItem, CacheExpiration);
     }
     public async Task<TMDBCacheItem> GetCacheItem(String key)
     {
@@ -32,4 +33,14 @@ public class TMDBCache
         else
             return null;
     }
+    public async Task<bool> KeyExists(String key)
+    {
+        var db = redis.GetDatabase();
+        return await db.KeyExistsAsync(key);
+    }
+    public async Task SetPair(String key, String value)
+    {
+        var db = redis.GetDatabase();
+        await db.StringSetAsync(key, value);
+    }
 }

AnimeAnnouncer/Program.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel;
+using System.Security.Cryptography;
 using AnimeAnnouncer.Cache;
 using AnimeAnnouncer.RSS;
 using Mastonet;
@@ -166,7 +167,16 @@ namespace AnimeAnnouncer
                 return;
             }
 
-            // Announce
+            // Announce if unique
+            if(await tmdbCache.KeyExists($"ShowAnnounced-{supposedShowId}"))
+            {
+                Console.WriteLine($"{title} has been previously announced, so avoiding announcing it again.");
+                return;
+            }
+            else
+            {
+                _ = tmdbCache.SetPair($"ShowAnnounced-{supposedShowId}", "1");
+            }
             if(mastodonClient != null)
             {
                 try