[fix] nullability warnings

Author: i4004

src/Etcd.Microsoft.Extensions.Configuration/Client/EtcdKeyValueClient.cs

@@ -25,7 +25,7 @@ public class EtcdKeyValueClient : IEtcdKeyValueClient
 	private readonly bool _enableWatch;
 	private readonly bool _unwatchOnDispose;
 
-	private readonly IList<long> _watchIDs = new List<long>();
+	private readonly IList<long> _watchIDs = [];
 	private readonly object _locker = new();
 
 	private string? _userName;
@@ -75,8 +75,7 @@ public EtcdKeyValueClient(IEtcdClientFactory clientFactory, ICredentials credent
 	/// <summary>
 	/// Gets all keys available to user.
 	/// </summary>
-	/// <returns></returns>
-	public IDictionary<string, string> GetAllKeys()
+	public IDictionary<string, string?> GetAllKeys()
 	{
 		CheckIsAuthenticated();
 
@@ -108,7 +107,6 @@ public IDictionary<string, string> GetAllKeys()
 	/// Gets the value.
 	/// </summary>
 	/// <param name="key">The key.</param>
-	/// <returns></returns>
 	public string? GetValue(string key)
 	{
 		CheckIsAuthenticated();
@@ -172,10 +170,7 @@ private IEnumerable<Permission> GetPermissions(string role) =>
 		}, GetMetadata()).Perm;
 
 	private Metadata GetMetadata() =>
-		new()
-		{
-			new("token", _token!)
-		};
+		[new Metadata.Entry("token", _token!)];
 
 	private void CheckIsAuthenticated()
 	{

src/Etcd.Microsoft.Extensions.Configuration/Client/IEtcdKeyValueClient.cs

@@ -27,7 +27,7 @@ public interface IEtcdKeyValueClient : IDisposable
 	/// Gets all keys available to user.
 	/// </summary>
 	/// <returns></returns>
-	IDictionary<string, string> GetAllKeys();
+	IDictionary<string, string?> GetAllKeys();
 
 	/// <summary>
 	/// Gets the value.

src/Etcd.Microsoft.Extensions.Configuration/EtcdConfigurationProvider.cs

@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using Microsoft.Extensions.Configuration;
 using Etcd.Microsoft.Extensions.Configuration.Client;
 using Etcd.Microsoft.Extensions.Configuration.Watch;
+using Microsoft.Extensions.Configuration;
 
 namespace Etcd.Microsoft.Extensions.Configuration;
 
@@ -43,7 +43,7 @@ public EtcdConfigurationProvider(IEtcdKeyValueClient client, string? keyPrefix =
 	/// <returns>
 	/// True if key has a value, false otherwise.
 	/// </returns>
-	public override bool TryGet(string key, out string value) =>
+	public override bool TryGet(string key, out string? value) =>
 		base.TryGet(_keyPrefix == null
 						? key
 						: _keyPrefix + ":" + key
@@ -53,7 +53,7 @@ public override bool TryGet(string key, out string value) =>
 	/// <param name="earlierKeys">The earlier keys that other providers contain.</param>
 	/// <param name="parentPath">The path for the parent IConfiguration.</param>
 	/// <returns>The list of keys for this provider.</returns>
-	public override IEnumerable<string> GetChildKeys(IEnumerable<string> earlierKeys, string parentPath) =>
+	public override IEnumerable<string> GetChildKeys(IEnumerable<string> earlierKeys, string? parentPath) =>
 		base.GetChildKeys(earlierKeys,
 			_keyPrefix != null
 				? _keyPrefix + ":" + parentPath

src/Etcd.Microsoft.Extensions.Configuration/Util/Convert.cs

@@ -15,14 +15,12 @@ public static class Convert
 	/// Converts the KeyValue list  to dictionary.
 	/// </summary>
 	/// <param name="list">The list.</param>
-	/// <returns></returns>
-	public static IDictionary<string, string> ToDictionary(IList<KeyValue> list) => list.ToDictionary(x => x.Key.ToStringUtf8(), x => x.Value.ToStringUtf8());
+	public static IDictionary<string, string?> ToDictionary(IList<KeyValue> list) => list.ToDictionary(x => x.Key.ToStringUtf8(), x => x.Value?.ToStringUtf8());
 
 	/// <summary>
 	/// Converts dotnet-etcd EventType to to local EventType.
 	/// </summary>
 	/// <param name="sourceType">Type of the source.</param>
-	/// <returns></returns>
 	public static EventType ToEventType(Event.Types.EventType sourceType) =>
 		sourceType switch
 		{