Solution_id is integer

[sunce86]

Description

Related to #3064

This PR enables driver to send either string or integer for solution_id.

This PR marks the start of transition period. Once the PR is merged, external solvers will be asked to:

1. Start sending solution_id as integer in /solve response.
2. Implement receiving either string or integer for solution_id on /reveal and on /settle.

Once done, backend will have a follow up where we will definitely switch to using integers in all three endpoints and #3064 will be fixed.

How to test

Manually checked that both versions are properly serialized/deserialized.

[squadgazzz]

LGTM

[m-lord-renkse]

Nice change!!

[MartinquaXD]

Alternatively this can also be implemented using a helper enum. Might be a bit more self explanatory.

fn deserialize_solution_id<'de, D>(deserializer: D) -> Result<u64, D::Error>
where
    D: serde::Deserializer<'de>,
{
    #[serde_as]
    #[derive(Deserialize, Debug)]
    #[serde(untagged)]
    enum StringOrInt {
        String(#[serde_as(as = "DisplayFromStr")] u64),
        Int(u64)
    }

    let result = match StringOrInt::deserialize(deserializer)? {
        StringOrInt::String(id) => id,
        StringOrInt::Int(id) => id
    };

    Ok(result)
}

[sunce86]

This one is nice as well. But I guess it's ok keeping the current version since it will be removed in one week from now.