Reduce method complexity in /ban, /unban and some other commands (#50)

This PR does numerous things to reduce method complexity:
- Created an extension method
`FeedbackService#SendContextualEmbedResultAsync`, which directly takes a
`Result<Embed>` and checks it once in the extension method instead of
multiple times in all commands;
- Split the command methods for `/ban` and `/unban` into 2 parts:
`Execute(Un)Ban` and `(Un)BanUserAsync`. The former will check all the
needed results and will pass the outputs into the latter;
- Extracted the method for logging an action into Private- and
PublicFeedbackChannels. It now resides in UtilityService. Right now,
only `/ban` and `/unban` make use of that method;
- Created an extension method `Snowflake#EmptyOrEqualTo`, that combines
the task of checking if a Snowflake is empty and checking if that
Snowflake is equal to another Snowflake.

Similar changes will be made to other command groups in future PRs. This
is not done here to make the reviewing process easier.

Signed-off-by: Octol1ttle <l1ttleofficial@outlook.com>

src/Extensions.cs

@@ -7,9 +7,11 @@ using Remora.Discord.API.Abstractions.Objects;
 using Remora.Discord.API.Objects;
 using Remora.Discord.Commands.Contexts;
 using Remora.Discord.Commands.Extensions;
+using Remora.Discord.Commands.Feedback.Services;
 using Remora.Discord.Extensions.Embeds;
 using Remora.Discord.Extensions.Formatting;
 using Remora.Rest.Core;
+using Remora.Results;
 
 namespace Boyfriend;
 
@@ -51,10 +53,9 @@ public static class Extensions {
     /// <param name="builder">The builder to add the small title to.</param>
     /// <param name="text">The text of the small title.</param>
     /// <param name="avatarSource">The user whose avatar to use in the small title.</param>
-    /// <param name="url">The URL that will be opened if a user clicks on the small title.</param>
     /// <returns>The builder with the added small title in the author field.</returns>
     public static EmbedBuilder WithSmallTitle(
-        this EmbedBuilder builder, string text, IUser? avatarSource = null, string? url = default) {
+        this EmbedBuilder builder, string text, IUser? avatarSource = null) {
         Uri? avatarUrl = null;
         if (avatarSource is not null) {
             var avatarUrlResult = CDN.GetUserAvatarUrl(avatarSource, imageSize: 256);
@@ -64,7 +65,7 @@ public static class Extensions {
                 : CDN.GetDefaultUserAvatarUrl(avatarSource, imageSize: 256).Entity;
         }
 
-        builder.Author = new EmbedAuthorBuilder(text, url, avatarUrl?.AbsoluteUri);
+        builder.Author = new EmbedAuthorBuilder(text, iconUrl: avatarUrl?.AbsoluteUri);
         return builder;
     }
 
@@ -191,7 +192,35 @@ public static class Extensions {
                && context.TryGetUserID(out userId);
     }
 
+    /// <summary>
+    ///     Checks whether this Snowflake has any value set.
+    /// </summary>
+    /// <param name="snowflake">The Snowflake to check.</param>
+    /// <returns>true if the Snowflake has no value set or it's set to 0, false otherwise.</returns>
     public static bool Empty(this Snowflake snowflake) {
         return snowflake.Value is 0;
     }
+
+    /// <summary>
+    ///     Checks whether this snowflake is empty (see <see cref="Empty" />) or it's equal to
+    ///     <paramref name="anotherSnowflake" />
+    /// </summary>
+    /// <param name="snowflake">The Snowflake to check for emptiness</param>
+    /// <param name="anotherSnowflake">The Snowflake to check for equality with <paramref name="snowflake" />.</param>
+    /// <returns>
+    ///     true if <paramref name="snowflake" /> is empty or is equal to <paramref name="anotherSnowflake" />, false
+    ///     otherwise.
+    /// </returns>
+    /// <seealso cref="Empty" />
+    public static bool EmptyOrEqualTo(this Snowflake snowflake, Snowflake anotherSnowflake) {
+        return snowflake.Empty() || snowflake == anotherSnowflake;
+    }
+
+    public static async Task<Result> SendContextualEmbedResultAsync(
+        this FeedbackService feedback, Result<Embed> embedResult, CancellationToken ct = default) {
+        if (!embedResult.IsDefined(out var embed))
+            return Result.FromError(embedResult);
+
+        return (Result)await feedback.SendContextualEmbedAsync(embed, ct: ct);
+    }
 }