Allow the app to be configured to bypass the server selection screen. (#4131)

* Make account provider configuration more flexible.

- Change defaultHomeserverAddress to an array of providers (needs UI).
- Add allowOtherAccountProviders to prevent the user from manually entering a provider.

* Refactor QR code scan failures into a common type.

* Validate scanned QR codes against the allowed account providers.

* Hide the login flow on the QR code screen when restricted.

UnitTests/Sources/AuthenticationStartScreenViewModelTests.swift

@@ -18,6 +18,16 @@ class AuthenticationStartScreenViewModelTests: XCTestCase {
     var viewModel: AuthenticationStartScreenViewModel!
     var context: AuthenticationStartScreenViewModel.Context { viewModel.context }
     
+    override func setUp() {
+        AppSettings.resetAllSettings()
+        let appSettings = AppSettings()
+        ServiceLocator.shared.register(appSettings: appSettings)
+    }
+    
+    override func tearDown() {
+        AppSettings.resetAllSettings()
+    }
+    
     func testInitialState() async throws {
         // Given a view model that has no provisioning parameters.
         setupViewModel()
@@ -80,6 +90,44 @@ class AuthenticationStartScreenViewModelTests: XCTestCase {
         XCTAssertEqual(authenticationService.homeserver.value.loginMode, .password)
     }
     
+    func testSingleProviderOIDCState() async throws {
+        // Given a view model that for an app that only allows the use of a single provider that supports OIDC.
+        setAllowedAccountProviders(["company.com"])
+        setupViewModel()
+        XCTAssertEqual(authenticationService.homeserver.value.loginMode, .unknown)
+        XCTAssertEqual(client.urlForOidcOidcConfigurationPromptLoginHintCallsCount, 0)
+        
+        // When tapping the login button the authentication service should be used and the screen
+        // should request to continue the flow without any server selection needed.
+        let deferred = deferFulfillment(viewModel.actions) { $0.isLoginDirectlyWithOIDC }
+        context.send(viewAction: .login)
+        try await deferred.fulfill()
+        
+        XCTAssertEqual(clientBuilderFactory.makeBuilderSessionDirectoriesPassphraseClientSessionDelegateAppSettingsAppHooksCallsCount, 1)
+        XCTAssertEqual(client.urlForOidcOidcConfigurationPromptLoginHintCallsCount, 1)
+        XCTAssertEqual(client.urlForOidcOidcConfigurationPromptLoginHintReceivedArguments?.prompt, .consent)
+        XCTAssertEqual(client.urlForOidcOidcConfigurationPromptLoginHintReceivedArguments?.loginHint, nil)
+        XCTAssertEqual(authenticationService.homeserver.value.loginMode, .oidc(supportsCreatePrompt: false))
+    }
+    
+    func testSingleProviderPasswordState() async throws {
+        // Given a view model that for an app that only allows the use of a single provider that does not support OIDC.
+        setAllowedAccountProviders(["company.com"])
+        setupViewModel(supportsOIDC: false)
+        XCTAssertEqual(authenticationService.homeserver.value.loginMode, .unknown)
+        XCTAssertEqual(client.urlForOidcOidcConfigurationPromptLoginHintCallsCount, 0)
+        
+        // When tapping the login button the authentication service should be used and the screen
+        // should request to continue the flow without any server selection needed.
+        let deferred = deferFulfillment(viewModel.actions) { $0.isLoginDirectlyWithPassword }
+        context.send(viewAction: .login)
+        try await deferred.fulfill()
+        
+        // Then a call to configure service should be made.
+        XCTAssertEqual(clientBuilderFactory.makeBuilderSessionDirectoriesPassphraseClientSessionDelegateAppSettingsAppHooksCallsCount, 1)
+        XCTAssertEqual(authenticationService.homeserver.value.loginMode, .password)
+    }
+    
     // MARK: - Helpers
     
     private func setupViewModel(provisioningParameters: AccountProvisioningParameters? = nil, supportsOIDC: Bool = true) {
@@ -106,6 +154,28 @@ class AuthenticationStartScreenViewModelTests: XCTestCase {
         // Add a fake window in order for the OIDC flow to continue
         viewModel.context.send(viewAction: .updateWindow(UIWindow()))
     }
+    
+    private func setAllowedAccountProviders(_ providers: [String]) {
+        let appSettings: AppSettings! = ServiceLocator.shared.settings
+        appSettings.override(accountProviders: providers,
+                             allowOtherAccountProviders: false,
+                             pushGatewayBaseURL: appSettings.pushGatewayBaseURL,
+                             oidcRedirectURL: appSettings.oidcRedirectURL,
+                             websiteURL: appSettings.websiteURL,
+                             logoURL: appSettings.logoURL,
+                             copyrightURL: appSettings.copyrightURL,
+                             acceptableUseURL: appSettings.acceptableUseURL,
+                             privacyURL: appSettings.privacyURL,
+                             encryptionURL: appSettings.encryptionURL,
+                             deviceVerificationURL: appSettings.deviceVerificationURL,
+                             chatBackupDetailsURL: appSettings.chatBackupDetailsURL,
+                             identityPinningViolationDetailsURL: appSettings.identityPinningViolationDetailsURL,
+                             elementWebHosts: appSettings.elementWebHosts,
+                             accountProvisioningHost: appSettings.accountProvisioningHost,
+                             bugReportApplicationID: appSettings.bugReportApplicationID,
+                             analyticsTermsURL: appSettings.analyticsTermsURL,
+                             mapTilerConfiguration: appSettings.mapTilerConfiguration)
+    }
 }
 
 extension AuthenticationStartScreenViewModelAction {