Add support for a dataVariation

[mcmurrym]

Add times it would be nice if we could just get back a Data or representation of the value that is stored for a variation. This would help with https://github.com/launchdarkly/ios-client-sdk/issues/274.

Something like...

public func dataVariation<T: Decodable>(forKey flagKey: LDFlagKey, defaultValue: T) -> T {
    variationDetailInternal(flagKey, defaultValue, needsReason: false).value
}
public func dataVariationDetail<T: Decodable>(forKey flagKey: LDFlagKey, defaultValue: T) -> LDEvaluationDetail<T> {
    variationDetailInternal(flagKey, defaultValue, needsReason: true)
}
public func dataVariation(forKey flagKey: LDFlagKey, defaultValue: Data) -> Data {
    variationDetailInternal(flagKey, defaultValue, needsReason: false).value
}
public func dataVariationDetail(forKey flagKey: LDFlagKey, defaultValue: Data) -> LDEvaluationDetail<Data> {
    variationDetailInternal(flagKey, defaultValue, needsReason: true)
}

I would be more than happy to help create the solution, but because LDValue goes as deep as it does, it would take some non-insignificant changes.

[mkambale]

@mcmurrym I am badly struck in extracting the values. Please help me with this. I am using LaunchDarkly 6.0 and getting flag value as a dictionary. I am facing problem in reading the values from flag. This is how I am getting flag value from server -

    let arrayValue = LDClient.get()!.jsonVariationDetail(forKey: forFlag, defaultValue: ["enabled": false])

And, I get this response -

My problem is how do I read the values from arrayValue.value ? I need to make certain changes depending on the values from dictionary. cc: @@louis-launchdarkly

[louis-launchdarkly]

Given this is a solution suggestion for the concern in #274, we will keep the discussion there for now.

[brianmichel]

I just ran into this issue as well, and it's a big bummer that LD does not make these values easily codable. It would be great if they were just parsed out as a regular set of struct as needed @louis-launchdarkly

[keelerm84]

We just released v9.4.0 which adds two new methods variation<T> and variationDetail<T>! Both of these methods accept a type that must be Decodable and implement our LDValueConvertible protocol (required for now to deal with some internal plumbing).