Make default lax

Author: JunTaoLuo

src/Microsoft.AspNetCore.Http.Features/CookieOptions.cs

@@ -44,10 +44,10 @@ public CookieOptions()
 
 
         /// <summary>
-        /// Gets or sets the value for the SameSite attribute of the cookie.
+        /// Gets or sets the value for the SameSite attribute of the cookie. The default value is <see cref="SameSiteEnforcementMode.Lax"/>
         /// </summary>
         /// <returns>The <see cref="SameSiteEnforcementMode"/> representing the enforcement mode of the cookie.</returns>
-        public SameSiteEnforcementMode SameSite { get; set; }
+        public SameSiteEnforcementMode SameSite { get; set; } = SameSiteEnforcementMode.Lax;
 
         /// <summary>
         /// Gets or sets a value that indicates whether a cookie is accessible by client-side script.