Work on permission system, along with initial work on database(postgres) system

DeukBot4/Database/DatabaseConnection.cs

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+using System;
+using DeukBot4.MessageHandlers.Permissions;
+using Npgsql;
+
+namespace DeukBot4.Database
+{
+    public class DatabaseConnection : IDisposable
+    {
+        public static string ConnectionString { private get; set; }
+        private readonly NpgsqlConnection _connection;
+
+        public DatabaseConnection()
+        {
+            _connection = new NpgsqlConnection(ConnectionString);
+            _connection.Open();
+        }
+
+        public void Dispose()
+        {
+            _connection.Dispose();
+        }
+
+        public static implicit operator NpgsqlConnection(DatabaseConnection conn)
+        {
+            return conn._connection;
+        }
+    }
+}

DeukBot4/Database/DatabaseInitializer.cs

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+using Npgsql;
+
+namespace DeukBot4.Database
+{
+    public static class DatabaseInitializer
+    {
+        public static void Initialize()
+        {
+            using (var conn = new DatabaseConnection())
+            {
+                using (var cmd = new NpgsqlCommand())
+                {
+                    cmd.Connection = conn;
+                    cmd.CommandText = "CREATE TABLE IF NOT EXISTS permission_roles (" +
+                                      "server_id bigint NOT NULL," +
+                                      "role_id bigint NOT NULL," +
+                                      "permission_level smallint NOT NULL," +
+                                      "PRIMARY KEY(server_id, role_id)" +
+                                      ")";
+                    cmd.ExecuteNonQuery();
+                }
+            }
+        }
+    }
+}

DeukBot4/Database/DatabaseRolePermissions.cs

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+using System.Threading.Tasks;
+using DeukBot4.MessageHandlers.Permissions;
+using DeukBot4.Utilities;
+using Npgsql;
+
+namespace DeukBot4.Database
+{
+    public static class DatabaseRolePermissions
+    {
+        public static async Task SetRolePermission(ulong serverId, ulong roleId, PermissionLevel permissionLevel)
+        {
+            using (var conn = new DatabaseConnection())
+            {
+                using (var cmd = new NpgsqlCommand())
+                {
+                    cmd.Connection = conn;
+                    cmd.CommandText = "INSERT INTO permission_roles (server_id, role_id, permission_level)" +
+                                      "VALUES (@server_id, @role_id, @permission_level) " +
+                                      "ON CONFLICT (server_id, role_id) DO UPDATE SET permission_level = @permission_level";
+                    cmd.Parameters.AddWithValue("server_id", serverId.ToLong());
+                    cmd.Parameters.AddWithValue("role_id", roleId.ToLong());
+                    cmd.Parameters.AddWithValue("permission_level", (sbyte)permissionLevel);
+                    await cmd.ExecuteNonQueryAsync();
+                }
+            }
+        }
+
+        public static async Task<PermissionLevel> GetRolePermission(ulong serverId, ulong roleId)
+        {
+            using (var conn = new DatabaseConnection())
+            {
+                using (var cmd = new NpgsqlCommand())
+                {
+                    cmd.Connection = conn;
+                    cmd.CommandText =
+                        "SELECT permission_level FROM permission_roles WHERE server_id = @server_id AND role_id = @role_id";
+                    cmd.Parameters.AddWithValue("server_id", serverId.ToLong());
+                    cmd.Parameters.AddWithValue("role_id", roleId.ToLong());
+
+                    var reader = cmd.ExecuteReader();
+                    while (await reader.ReadAsync())
+                    {
+                        return (PermissionLevel)(sbyte)reader.GetInt16(0);
+                    }
+
+                    return (PermissionLevel)sbyte.MinValue;
+                }
+            }
+        }
+    }
+}