fix: re-added a missing extension method

src/NadekoBot/_common/Abstractions/Extensions/SelfAssignableRolesExtensions.cs

@@ -0,0 +1,23 @@
+using Microsoft.EntityFrameworkCore;
+using NadekoBot.Db.Models;
+
+namespace NadekoBot.Db;
+
+public static class SelfAssignableRolesExtensions
+{
+    public static bool DeleteByGuildAndRoleId(this DbSet<SelfAssignedRole> roles, ulong guildId, ulong roleId)
+    {
+        var role = roles.FirstOrDefault(s => s.GuildId == guildId && s.RoleId == roleId);
+
+        if (role is null)
+            return false;
+
+        roles.Remove(role);
+        return true;
+    }
+
+    public static IReadOnlyCollection<SelfAssignedRole> GetFromGuild(
+        this DbSet<SelfAssignedRole> roles,
+        ulong guildId)
+        => roles.AsQueryable().Where(s => s.GuildId == guildId).ToArray();
+}