User duplicated error should come before password check

[rickmak]

On registering a duplicated user, he will first got password complexity error before user duplicate error.

• Skygear Server Date/Version: v1.3.1-36-g37291e0
• Application Platform:
• [ ] Is this a regression?
• [ ] Attached logs, screenshots

Expected Results

If an existing user try to signin again. He will got user duplicated error regardless what password he provided.

Actual Results

Password complexity error comes first, user duplicated error comes after.

Steps to reproduce

1. Signup an account

{
    "action": "auth:signup",
    "api_key": "som_api_key",
    "auth_data": {
        "email": "[email protected]"
    },
    "password": "!@#$%^"
}

{
    "action": "auth:signup",
    "api_key": "som_api_key",
    "auth_data": {
        "email": "[email protected]"
    },
    "password": "123456"
}

Response (Or other password check error)

{
    "error": {
        "code": 132,
        "message": "password containing excluded keywords",
        "name": "PasswordContainingExcludedKeywords"
    }
}

{
    "action": "auth:signup",
    "api_key": "som_api_key",
    "auth_data": {
        "email": "[email protected]"
    },
    "password": "123456"
}

Response

{
    "error": {
        "code": 109,
        "message": "user duplicated",
        "name": "Duplicated"
    }
}