Add Authentication Flow WIP.

- Add Registration Screen.
- Add Server Selection Screen.
- Rename AuthenticationCoordinator to LegacyAuthenticationCoordinator.
- Add AuthenticationService and RegistrationWizard.
- Async extensions.
- Add global white and EMS colors to the themes.
- Add tests for server selection and registration screens.
- Accessibility and iPad layout tweaks.
- Remove MainActor from Auth Coordinators/VMs/Views.
(It broke the protocol conformances so now the methods and properties are marked individually.)

RiotSwiftUI/Modules/Authentication/Registration/MockAuthenticationRegistrationScreenState.swift

@@ -0,0 +1,78 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import SwiftUI
+
+/// Using an enum for the screen allows you define the different state cases with
+/// the relevant associated data for each case.
+@available(iOS 14.0, *)
+enum MockAuthenticationRegistrationScreenState: MockScreenState, CaseIterable {
+    // A case for each state you want to represent
+    // with specific, minimal associated data that will allow you
+    // mock that screen.
+    case matrixDotOrg
+    case passwordOnly
+    case passwordWithCredentials
+    case passwordWithUsernameError
+    case ssoOnly
+
+    /// The associated screen
+    var screenType: Any.Type {
+        AuthenticationRegistrationScreen.self
+    }
+
+    /// Generate the view struct for the screen state.
+    var screenView: ([Any], AnyView)  {
+        let viewModel: AuthenticationRegistrationViewModel
+        switch self {
+        case .matrixDotOrg:
+            viewModel = AuthenticationRegistrationViewModel(homeserverAddress: "https://matrix.org", ssoIdentityProviders: [
+                SSOIdentityProvider(id: "1", name: "Apple", brand: "apple", iconURL: nil),
+                SSOIdentityProvider(id: "2", name: "Facebook", brand: "facebook", iconURL: nil),
+                SSOIdentityProvider(id: "3", name: "GitHub", brand: "github", iconURL: nil),
+                SSOIdentityProvider(id: "4", name: "GitLab", brand: "gitlab", iconURL: nil),
+                SSOIdentityProvider(id: "5", name: "Google", brand: "google", iconURL: nil)
+            ])
+        case .passwordOnly:
+            viewModel = AuthenticationRegistrationViewModel(homeserverAddress: "https://example.com", ssoIdentityProviders: [])
+        case .passwordWithCredentials:
+            viewModel = AuthenticationRegistrationViewModel(homeserverAddress: "https://example.com", ssoIdentityProviders: [])
+            viewModel.context.username = "alice"
+            viewModel.context.password = "password"
+        case .passwordWithUsernameError:
+            viewModel = AuthenticationRegistrationViewModel(homeserverAddress: "https://example.com", ssoIdentityProviders: [])
+            viewModel.state.hasEditedUsername = true
+            Task {
+                await MainActor.run {
+                    viewModel.displayError(.usernameUnavailable(VectorL10n.authInvalidUserName))
+                }
+            }
+        case .ssoOnly:
+            // TODO: As part of the login flow the screen should be shared and made be more configurable. Right now password registration is hard coded in.
+            viewModel = AuthenticationRegistrationViewModel(homeserverAddress: "https://company.com", ssoIdentityProviders: [
+                SSOIdentityProvider(id: "test", name: "SAML", brand: nil, iconURL: nil)
+            ])
+        }
+        
+
+        // can simulate service and viewModel actions here if needs be.
+
+        return (
+            [viewModel], AnyView(AuthenticationRegistrationScreen(viewModel: viewModel.context))
+        )
+    }
+}