[BUG] User registration via real-time API happens with invalid custom fields

Description:

Even if the server returns "error-user-registration-custom-field", the user is still registered without the invalid fields.

Server Setup Information:

• Version of Rocket.Chat Server: 0.58.2
• Deployment Method(snap/docker/tar/etc): rocket.chat/hosting

Steps to Reproduce:

1. Setup a custom field like

"role":{  
      "type":"select",
      "defaultValue":"student",
      "options":[  
         "teacher",
         "student"
      ],
      "required":true,
      "modifyRecordField":{  
         "array":true,
         "field":"roles"
      }
   }

2. Register a user using the Real-Time API with an invalid option, eg. "god" when there's no such option or empty when the field is required.

3. Notice the user has been registered (without the invalid fields)

This is probably not happening on the web version as it's displaying a nice dropdown, but IMO the API should prevent this from happening.

Expected behavior:

The API should return an error and not register the user

Actual behavior:

The API returns an error but still register the user without the invalid fields

Start at the Real-Time API user-registration entry point and reproduce the custom-field cases described: an invalid option and an empty required field. Trace the error path to confirm registration is not committed when validation fails; done means invalid requests return the error without creating a user or silently dropping fields.