refactor: move extensions to extensions file

src/Intility.Authorization.Azure.GuestPolicies/Policy/DenyGuestsAuthorizationsHandler.cs

@@ -58,20 +58,3 @@ protected override Task HandleRequirementAsync(AuthorizationHandlerContext conte
         return claimsPrincipal.FindFirstValue(IdentityProvider) ?? claimsPrincipal.FindFirstValue(Idp) ?? issuer;
     }
 }
-
-/// <summary>
-/// Contains extension methods for denying guests.
-/// </summary>
-public static class DenyGuestsAuthorizationExtensions
-{
-    /// <summary>
-    /// Adds a requirement to the policy builder that denies guests.
-    /// </summary>
-    /// <param name="builder">The authorization policy builder.</param>
-    /// <returns>The same builder instance.</returns>
-    public static AuthorizationPolicyBuilder DenyGuests(this AuthorizationPolicyBuilder builder)
-    {
-        builder.AddRequirements(new DenyGuestsAuthorizationRequirement());
-        return builder;
-    }
-}

src/Intility.Authorization.Azure.GuestPolicies/Policy/DenyGuestsExtensions.cs

@@ -22,4 +22,18 @@ public static IServiceCollection AddDenyGuestsAuthorization(this IServiceCollect
 
         return services;
     }
+
+    /// <summary>
+    /// Adds a <see cref="DenyGuestsAuthorizationRequirement"/> to the current instance which requires that the current user is a member of the tenant.
+    /// </summary>
+    /// <param name="authorizationPolicyBuilder">Used for building policies during application startup.</param>
+    /// <returns>A reference to this instance after the operation has completed.</returns>
+    public static AuthorizationPolicyBuilder DenyGuests(this AuthorizationPolicyBuilder authorizationPolicyBuilder)
+    {
+        ArgumentNullException.ThrowIfNull(authorizationPolicyBuilder);
+
+        authorizationPolicyBuilder.Requirements.Add(new DenyGuestsAuthorizationRequirement());
+
+        return authorizationPolicyBuilder;
+    }
 }