(core) Trigger email verification flow when needed

Summary:
When an unconfirmed user tries to sign in or reset their password, the email
verification flow is now automatically restarted. Prior to this change, an
unconfirmed user error was shown in the client.

Test Plan: Deployment tests.

Reviewers: paulfitz, dsagal

Reviewed By: dsagal

Subscribers: dsagal

Differential Revision: https://phab.getgrist.com/D4133

app/common/ApiError.ts

@@ -23,6 +23,8 @@ export interface ApiLimit {
  * Structured details about an API error.
  */
 export interface ApiErrorDetails {
+  code?: ApiErrorCode;
+
   limit?: ApiLimit;
 
   // If set, this is the more user-friendly message to show to the user than error.message.
@@ -34,6 +36,9 @@ export interface ApiErrorDetails {
   memos?: string[];
 }
 
+export type ApiErrorCode =
+  | 'UserNotConfirmed';
+
 /**
  * An error with an http status code.
  */