fix(auth): use auth flow type correctly from amplifyconfiguraiton.json (#3928)

Author: harsh62

AmplifyPlugins/Auth/Sources/AWSCognitoAuthPlugin/Models/AuthFlowType.swift

@@ -34,6 +34,21 @@ public enum AuthFlowType {
     /// - `preferredFirstFactor`: the auth factor type the user should begin signing with if available. If the preferred first factor is not available, the flow would fallback to provide available first factors.
     case userAuth(preferredFirstFactor: AuthFactorType?)
 
+    internal init?(rawValue: String) {
+        switch rawValue {
+        case "CUSTOM_AUTH":
+            self = .customWithSRP
+        case "USER_SRP_AUTH":
+            self = .userSRP
+        case "USER_PASSWORD_AUTH":
+            self = .userPassword
+        case "USER_AUTH":
+            self = .userAuth
+        default:
+            return nil
+        }
+    }
+
     var rawValue: String {
         switch self {
         case .custom, .customWithSRP, .customWithoutSRP:

AmplifyPlugins/Auth/Sources/AWSCognitoAuthPlugin/Support/Helpers/ConfigurationHelper.swift

@@ -47,14 +47,17 @@ struct ConfigurationHelper {
 
         // parse `authFlowType`
         var authFlowType: AuthFlowType
+
+        // If Migration path is enabled, auth flow type should always be set to USER_PASSWORD_AUTH
         if case .boolean(let isMigrationEnabled) = cognitoUserPoolJSON.value(at: "MigrationEnabled"),
            isMigrationEnabled == true {
             authFlowType = .userPassword
         } else if let authJson = config.value(at: "Auth.Default"),
-                  case .string(let authFlowTypeJSON) = authJson.value(at: "authenticationFlowType"),
-                  authFlowTypeJSON == "CUSTOM_AUTH" {
-            authFlowType = .customWithSRP
+                  case .string(let authFlowTypeConfigValue) = authJson.value(at: "authenticationFlowType"),
+                  let authFlowTypeFromConfig = AuthFlowType(rawValue: authFlowTypeConfigValue) {
+            authFlowType = authFlowTypeFromConfig
         } else {
+            // if the auth flow type is not found from config, default to SRP
             authFlowType = .userSRP
         }