fix: warning issues resolved

Author: OMpawar-21

Contentstack.Management.Core/ContentstackClient.cs

@@ -581,7 +581,7 @@ public bool HasValidOAuthTokens(string clientId)
         /// This method should be called when logging out or switching authentication methods.
         /// </summary>
         /// <param name="clientId">The OAuth client ID to clear tokens for.</param>
-        public void ClearOAuthTokens(string clientId = null)
+        public void ClearOAuthTokens(string? clientId = null)
         {
             if (!string.IsNullOrEmpty(clientId))
             {

Contentstack.Management.Core/Models/Extension.cs

@@ -10,11 +10,11 @@ namespace Contentstack.Management.Core.Models
     public class Extension
     {
         internal Stack stack;
-        public string Uid { get; set; }
+        public string? Uid { get; set; }
 
         internal string resourcePath;
 
-        internal Extension(Stack stack, string uid = null)
+        internal Extension(Stack stack, string? uid = null)
         {
             stack.ThrowIfAPIKeyEmpty();
 
@@ -153,7 +153,7 @@ public virtual ContentstackResponse Update(ExtensionModel model)
         /// </code></pre>
         /// </example>
         /// <returns>The <see cref="ContentstackResponse"/>.</returns>
-        public virtual Task<ContentstackResponse> UpdateAsync(ExtensionModel model, ParameterCollection collection = null)
+        public virtual Task<ContentstackResponse> UpdateAsync(ExtensionModel model, ParameterCollection? collection = null)
         {
             stack.ThrowIfNotLoggedIn();
             ThrowIfUidEmpty();
@@ -173,7 +173,7 @@ public virtual Task<ContentstackResponse> UpdateAsync(ExtensionModel model, Para
         /// </code></pre>
         /// </example>
         /// <returns>The <see cref="ContentstackResponse"/>.</returns>
-        public virtual ContentstackResponse Fetch(ParameterCollection collection = null)
+        public virtual ContentstackResponse Fetch(ParameterCollection? collection = null)
         {
             stack.ThrowIfNotLoggedIn();
             ThrowIfUidEmpty();
@@ -193,7 +193,7 @@ public virtual ContentstackResponse Fetch(ParameterCollection collection = null)
         /// </code></pre>
         /// </example>
         /// <returns>The <see cref="ContentstackResponse"/>.</returns>
-        public virtual Task<ContentstackResponse> FetchAsync(ParameterCollection collection = null)
+        public virtual Task<ContentstackResponse> FetchAsync(ParameterCollection? collection = null)
         {
             stack.ThrowIfNotLoggedIn();
             ThrowIfUidEmpty();

Contentstack.Management.Core/Models/Stack.cs

@@ -675,7 +675,7 @@ public GlobalField GlobalField(string? uid = null, string? apiVersion = null)
         /// </code></pre>
         /// </example>
         /// <returns>The <see cref="Models.Extension" /></returns>
-        public Extension Extension(string uid = null)
+        public Extension Extension(string? uid = null)
         {
             ThrowIfNotLoggedIn();
             ThrowIfAPIKeyEmpty();
@@ -917,7 +917,7 @@ public Webhook Webhook(string? uid = null)
         /// </code></pre>
         /// </example>
         /// <returns>The <see cref="Models.AuditLog" /></returns>
-        public AuditLog AuditLog(string uid = null)
+        public AuditLog AuditLog(string? uid = null)
         {
             ThrowIfNotLoggedIn();
             ThrowIfAPIKeyEmpty();

Contentstack.Management.Core/Services/OAuth/OAuthAppRevocationService.cs

@@ -11,7 +11,7 @@ internal class OAuthAppRevocationService : ContentstackService
     {
         private readonly string _appId;
         private readonly string _authorizationId;
-        private readonly string _organizationUid;
+        private readonly string? _organizationUid;
 
         /// <summary>
         /// Initializes a new instance of the OAuthAppRevocationService class.
@@ -20,7 +20,7 @@ internal class OAuthAppRevocationService : ContentstackService
         /// <param name="appId">The OAuth app ID.</param>
         /// <param name="authorizationId">The authorization ID to revoke.</param>
         /// <param name="organizationUid">The organization UID for OAuth operations.</param>
-        internal OAuthAppRevocationService(JsonSerializerOptions serializer, string appId, string authorizationId, string organizationUid = null)
+        internal OAuthAppRevocationService(JsonSerializerOptions serializer, string appId, string authorizationId, string? organizationUid = null)
             : base(serializer)
         {
             if (string.IsNullOrEmpty(appId))

Contentstack.Management.Core/Services/OAuth/OAuthTokenService.cs

@@ -68,7 +68,7 @@ public override void ContentBody()
         /// <param name="addAcceptMediaHeader">Whether to add accept media headers.</param>
         /// <param name="apiVersion">The API version to use.</param>
         /// <returns>The HTTP request for OAuth token operations.</returns>
-        public override IHttpRequest CreateHttpRequest(System.Net.Http.HttpClient httpClient, ContentstackClientOptions config, bool addAcceptMediaHeader = false, string apiVersion = null)
+        public override IHttpRequest CreateHttpRequest(System.Net.Http.HttpClient httpClient, ContentstackClientOptions config, bool addAcceptMediaHeader = false, string? apiVersion = null)
         {
             // Create a custom config with Developer Hub hostname for OAuth token operations
             // OAuth token endpoints don't use API versioning, so we set Version to empty
@@ -151,8 +151,8 @@ public static OAuthTokenService CreateForAuthorizationCode(
             string authorizationCode,
             string clientId,
             string redirectUri,
-            string clientSecret = null,
-            string codeVerifier = null)
+            string? clientSecret = null,
+            string? codeVerifier = null)
         {
             if (string.IsNullOrEmpty(authorizationCode))
                 throw new ArgumentException("Authorization code cannot be null or empty.", nameof(authorizationCode));
@@ -231,7 +231,7 @@ public static OAuthTokenService CreateForRefreshToken(
             JsonSerializerOptions serializer,
             string refreshToken,
             string clientId,
-            string clientSecret = null)
+            string? clientSecret = null)
         {
             if (string.IsNullOrEmpty(refreshToken))
                 throw new ArgumentException("Refresh token cannot be null or empty.", nameof(refreshToken));