Ensure consequence.params.ignorePlurals can be deserialized from string

[aseure]

It was discovered that the Algolia Search API is sometimes returning the
ignorePlurals field from a Query Rule's consequence params field as a
string, such as:

"consequence": {
    "params": {
        "ignorePlurals": "false"
    }
}

Could you please ensure that the deserialization of query rules coming from
getRule, getRules, browseRules are correctly decoding those strings
without failing.

Also, like we did for other string-based booleans, it would be convenient to
convert the string to an actual boolean when the string is equal to "true" or
"false".