[Swift] Stop emitting ec_color_scheme query param

Part of https://github.com/shop/issues-checkout-kit/issues/906.
The Checkout Kits will no longer thread color scheme through ECP. This PR strips ec_color_scheme emission from the Swift kit:

- CheckoutProtocol.url(for:): drop the colorScheme parameter and the
  ec_color_scheme queryItem; ec_version still emitted
- CheckoutViewController.init and ShopifyCheckoutKit.preload/present:
  drop the colorScheme argument at the 4 call sites

CheckoutProtocol.url(for:colorScheme:) is public but PR #65 has not yet
been released (no 3.8.0 tag), so removing the parameter outright is safe.
Android equivalent landed in #95.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Juanita-Dash

platforms/swift/Sources/ShopifyCheckoutKit/CheckoutViewController.swift

@@ -57,7 +57,7 @@ public struct CheckoutSheet: UIViewControllerRepresentable, CheckoutConfigurable
     var onFailAction: ((CheckoutError) -> Void)?
 
     public init(checkout url: URL) {
-        checkoutURL = CheckoutProtocol.url(for: url, colorScheme: ShopifyCheckoutKit.configuration.colorScheme.rawValue)
+        checkoutURL = CheckoutProtocol.url(for: url)
 
         ShopifyCheckoutKit.invalidateOnConfigurationChange = false
     }

platforms/swift/Sources/ShopifyCheckoutKit/ShopifyCheckoutKit.swift

@@ -52,7 +52,7 @@ public func preload(checkout url: URL) {
         return
     }
 
-    let url = CheckoutProtocol.url(for: url, colorScheme: configuration.colorScheme.rawValue)
+    let url = CheckoutProtocol.url(for: url)
     CheckoutWebView.preloadingActivatedByClient = true
     CheckoutWebView.for(checkout: url).load(checkout: url, isPreload: true)
 }
@@ -64,15 +64,15 @@ public func invalidate() {
 
 @discardableResult
 public func present(checkout url: URL, from: UIViewController, client: (any CheckoutCommunicationProtocol)? = nil) -> CheckoutViewController {
-    let decorated = CheckoutProtocol.url(for: url, colorScheme: configuration.colorScheme.rawValue)
+    let decorated = CheckoutProtocol.url(for: url)
     let viewController = CheckoutViewController(checkout: decorated, client: client)
     from.present(viewController, animated: true)
     return viewController
 }
 
 @discardableResult
 package func present(checkout url: URL, from: UIViewController, entryPoint: MetaData.EntryPoint, client: (any CheckoutCommunicationProtocol)? = nil) -> CheckoutViewController {
-    let decorated = CheckoutProtocol.url(for: url, colorScheme: configuration.colorScheme.rawValue)
+    let decorated = CheckoutProtocol.url(for: url)
     let viewController = CheckoutViewController(checkout: decorated, client: client, entryPoint: entryPoint)
     from.present(viewController, animated: true)
     return viewController

platforms/swift/Sources/ShopifyCheckoutProtocol/CheckoutProtocol+URL.swift

@@ -25,15 +25,13 @@ import Foundation
 
 extension CheckoutProtocol {
     /// Returns the given checkout URL with the query parameters required to
-    /// initiate the Embedded Checkout Protocol handshake (`ec_version`,
-    /// `ec_color_scheme`).
-    public static func url(for url: URL, colorScheme: String) -> URL {
+    /// initiate the Embedded Checkout Protocol handshake (`ec_version`).
+    public static func url(for url: URL) -> URL {
         guard var components = URLComponents(url: url, resolvingAgainstBaseURL: false) else {
             return url
         }
         var queryItems = components.queryItems ?? []
         queryItems.append(URLQueryItem(name: "ec_version", value: specVersion))
-        queryItems.append(URLQueryItem(name: "ec_color_scheme", value: colorScheme))
         components.queryItems = queryItems
         return components.url ?? url
     }

platforms/swift/Tests/ShopifyCheckoutProtocolTests/CheckoutProtocolURLTests.swift

@@ -0,0 +1,55 @@
+/*
+ MIT License
+
+ Copyright 2023 - Present, Shopify Inc.
+
+ Permission is hereby granted, free of charge, to any person obtaining a copy
+ of this software and associated documentation files (the "Software"), to deal
+ in the Software without restriction, including without limitation the rights
+ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ copies of the Software, and to permit persons to whom the Software is
+ furnished to do so, subject to the following conditions:
+
+ The above copyright notice and this permission notice shall be included in all
+ copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+import Foundation
+@testable import ShopifyCheckoutProtocol
+import Testing
+
+@Suite("CheckoutProtocol URL Tests")
+struct CheckoutProtocolURLTests {
+    private let baseURL = URL(string: "https://shop.com/cart/c/abc")!
+
+    private func queryItems(_ url: URL) -> [URLQueryItem] {
+        URLComponents(url: url, resolvingAgainstBaseURL: false)?.queryItems ?? []
+    }
+
+    @Test func appendsEcVersion() {
+        let result = CheckoutProtocol.url(for: baseURL)
+        let items = queryItems(result)
+        #expect(items.contains(URLQueryItem(name: "ec_version", value: CheckoutProtocol.specVersion)))
+    }
+
+    @Test func doesNotEmitEcColorScheme() {
+        let result = CheckoutProtocol.url(for: baseURL)
+        let names = queryItems(result).map(\.name)
+        #expect(names.contains("ec_color_scheme") == false)
+    }
+
+    @Test func preservesExistingQueryItems() throws {
+        let url = try #require(URL(string: "https://shop.com/cart/c/abc?key=cart_token&utm_source=email"))
+        let items = queryItems(CheckoutProtocol.url(for: url))
+        #expect(items.contains(URLQueryItem(name: "key", value: "cart_token")))
+        #expect(items.contains(URLQueryItem(name: "utm_source", value: "email")))
+        #expect(items.contains(URLQueryItem(name: "ec_version", value: CheckoutProtocol.specVersion)))
+    }
+}