Added signed up options for role reminder

Added option to opt out of reminders

DiscordBot/Messages/ReminderSubscriptionMessage.cs

@@ -0,0 +1,32 @@
+using Discord;
+using Discord.WebSocket;
+
+namespace DiscordBot.Messages
+{
+    public class ReminderSubscriptionMessage
+    {
+        public static async Task sendMessage(DiscordSocketClient client, ulong userId)
+        {
+            var builder = new ComponentBuilder()
+                .WithButton("Opt Out", $"{Constants.ComponentIds.OPT_OUT_BUTTON}", ButtonStyle.Danger);
+            
+            string message = "Hi, I'm Raid-o-Tron. \n"
+                            + "I will send you reminders for raids you have signed up for.\n"
+                            + "The reminders will look like\n"
+                            + "> Testraid: The raid starts in 30 minutes. \n"
+                            + "You can opt out of the reminders here or change it any time at https://lieb.games \n"
+                            + " ------------------------------------------- \n"
+                            + "Hi, ich bin Raid-o-Tron. \n"
+                            + "Ich werde dir Erinnerungen für Raid an denen du dich angemeldet hast schicken.\n"
+                            + "Die Erinnerungen werden so aussehen:\n"
+                            + "> Testraid: The raid starts in 30 minutes. \n"
+                            + "Du kannst dich von den Erinnerungen hier abmelden oder deine Einstellungen jederzeit auf https://lieb.games ändern.";
+
+            var user = await client.GetUserAsync(userId);
+            if(user != null)
+            {
+                await user.SendMessageAsync(message, components: builder.Build());
+            }
+        }
+    }
+}