Migration: properly handle field-specific errors.

src/MigrateV2.tsx

@@ -188,7 +188,24 @@ export function WizardAccountPage(props: OurPagePropsType & { setEtebase: (eteba
       props.next?.();
       setProgress("Done");
     } catch (e) {
-      if (e instanceof Etebase.UnauthorizedError) {
+      if ((e instanceof Etebase.HttpError) && (e.content)) {
+        let found = false;
+        if (e.content.errors) {
+          for (const field of e.content.errors) {
+            if (field.field === "user.username") {
+              errors.errorEmail = field.detail;
+              found = true;
+            } else if (!field.field) {
+              errors.errorGeneral = field.detail;
+              found = true;
+            }
+          }
+        }
+
+        if (!found) {
+          errors.errorGeneral = e.content.detail ?? e.toString();
+        }
+      } else if (e instanceof Etebase.UnauthorizedError) {
         errors.errorGeneral = "Wrong username or password";
       } else {
         errors.errorGeneral = e.toString();