Don't alarm on "Email in use" response from Identity /guest endpoint (

#6745)

Sometimes POST /guest returns "Email in use" even though we already
checked whether the user existed by looking them up with GET /user
passing their email address. According to identity occasionally users
get into a weird state and this is a result of that. I think this should
still result in a 500 (it's not related to something the user has done)
but we don't want to alarm on it.

support-frontend/app/actions/CustomActionBuilders.scala

@@ -72,6 +72,7 @@ class CustomActionBuilders(
         emailProviderRejectedCode,
         invalidEmailAddressCode,
         recaptchaFailedCode,
+        emailAddressAlreadyTakenCode,
       )
       if (result.header.status == 500) {
         if (!ignoreList.contains(result.header.reasonPhrase.getOrElse(""))) {

support-frontend/app/controllers/CreateSubscriptionController.scala

@@ -233,10 +233,14 @@ class CreateSubscriptionController(
     )
   }
 
-  private def mapIdentityErrorToCreateSubscriptionError(identityError: IdentityError) =
+  private def mapIdentityErrorToCreateSubscriptionError(identityError: IdentityError): CreateSubscriptionError =
     identityError match {
       case EmailProviderRejected(_) => RequestValidationError(emailProviderRejectedCode)
       case InvalidEmailAddress(_) => RequestValidationError(invalidEmailAddressCode)
+      // We're mapping this to a ServerError because it shouldn't ever happen, but sometimes does. Even though we
+      // asked identity (in getOrCreateIdentityUser) whether the user exists first, sometimes we get an answer of no
+      // back but then attempting to create returns this error.
+      case EmailAddressAlreadyTaken(_) => ServerError(emailAddressAlreadyTakenCode)
       case OtherIdentityError(message, description, endpoint) =>
         endpoint match {
           case Some(GuestEndpoint) => ServerError(s"Identity error calling /guest: $message; $description")
@@ -345,6 +349,14 @@ class CreateSubscriptionController(
                 ),
                 body = writeable.toEntity(err.message),
               )
+            case ServerError(code) if code == emailAddressAlreadyTakenCode =>
+              Result(
+                header = new ResponseHeader(
+                  status = INTERNAL_SERVER_ERROR,
+                  reasonPhrase = Some(emailAddressAlreadyTakenCode),
+                ),
+                body = writeable.toEntity(emailAddressAlreadyTakenCode),
+              )
             case _: ServerError =>
               InternalServerError
           }

support-frontend/app/models/identity/responses/IdentityErrorResponse.scala

@@ -28,13 +28,15 @@ object IdentityErrorResponse {
   implicit val reads: Reads[IdentityErrorResponse] = Json.reads[IdentityErrorResponse]
   val emailProviderRejectedCode = "email_provider_rejected"
   val invalidEmailAddressCode = "invalid_email_address"
+  val emailAddressAlreadyTakenCode = "email_address_already_taken"
 
   sealed trait IdentityError {
     def endpoint: Option[IdentityEndpoint]
     def setEndpoint(e: IdentityEndpoint): IdentityError = {
       this match {
         case EmailProviderRejected(_) => EmailProviderRejected(Some(e))
         case InvalidEmailAddress(_) => InvalidEmailAddress(Some(e))
+        case EmailAddressAlreadyTaken(_) => EmailAddressAlreadyTaken(Some(e))
         case OtherIdentityError(m, d, _endpoint) => OtherIdentityError(m, d, endpoint = Some(e))
       }
     }
@@ -46,6 +48,9 @@ object IdentityErrorResponse {
   /** The email address is invalid. */
   case class InvalidEmailAddress(endpoint: Option[IdentityEndpoint]) extends IdentityError
 
+  /** The email address is already associated with an existing account. */
+  case class EmailAddressAlreadyTaken(endpoint: Option[IdentityEndpoint]) extends IdentityError
+
   /** Some other error occurred. */
   case class OtherIdentityError(message: String, description: String, endpoint: Option[IdentityEndpoint])
       extends IdentityError
@@ -65,6 +70,8 @@ object IdentityErrorResponse {
         EmailProviderRejected(endpoint = None)
       } else if (message == "Invalid emailAddress:" && description == "Please enter a valid email address") {
         InvalidEmailAddress(endpoint = None)
+      } else if (message == "Email in use" && description == "This email has already been taken") {
+        EmailAddressAlreadyTaken(endpoint = None)
       } else {
         OtherIdentityError(message, description, endpoint = None)
       }