bug(events): api events with event_type user aren't parsed correctly in clickhouse

[lsampras]

The api events with events type user aren't parsed correctly in the user table,
this happens due to there being duplicate keys in the json representation which is treated as invalid json by clickhouse

{
    "key_a": "abc",
    "key_b": "def",
    "key_b": "ghi"
}

This is treated as invalid json and the entire event is dropped by clickhouse,

in this case we have

pub enum ApiEventsType {
.........
    User {
        merchant_id: String, // This merchant_id field ends up being duplicate and causes invalid json
        user_id: String,
    },
......
}

for now we can remove the merchant_id from this enum variant to solve this issue