fix: Disable client when project token is missing

.changeset/quiet-masks-jump.md

@@ -0,0 +1,5 @@
+---
+"PostHog": patch
+---
+
+Disable the client without logging a project token error when the SDK is explicitly disabled or the project token is missing.

src/PostHog/Config/PostHogOptions.cs

@@ -1,4 +1,5 @@
 using Microsoft.Extensions.Options;
+using PostHog.Library;
 
 namespace PostHog;
 
@@ -26,6 +27,14 @@ public string? ProjectToken
 
     internal bool HasLegacyProjectApiKey => _projectApiKey is not null;
 
+    internal void Normalize()
+    {
+        _projectToken = _projectToken.NullIfEmpty();
+        _projectApiKey = _projectApiKey.NullIfEmpty();
+        PersonalApiKey = PersonalApiKey.NullIfEmpty();
+        HostUrl = HostUrl.NormalizeHostUrl();
+    }
+
     /// <summary>
     /// Obsolete alias for <see cref="ProjectToken"/>.
     /// </summary>
@@ -49,6 +58,15 @@ public string? ProjectApiKey
     /// </remarks>
     public string? PersonalApiKey { get; set; }
 
+    /// <summary>
+    /// Whether this client is disabled and should no-op instead of sending data to PostHog. (Default: false)
+    /// </summary>
+    /// <remarks>
+    /// Read once during <see cref="PostHogClient"/> construction. Mutating this after the client is
+    /// activated has no effect. Re-create the client to change the disabled state.
+    /// </remarks>
+    public bool Disabled { get; set; }
+
     /// <summary>
     /// PostHog API host, usually 'https://us.i.posthog.com' (default) or 'https://eu.i.posthog.com'
     /// </summary>