feat(variants): allow in-memory objects

[Степан (Stepami)]

Why this PR?

Implementing IFeatureDefinitionProvider makes it inconvinient to fill variant bound values if they don't come from configuration.

Similarly to feature filters I decided to introduce an object that can be used as an alternative ConfigurationValue. Custom IFeatureDefinitionProvider implementations can populate this property directly instead of constructing an IConfigurationSection instance.

Visible Changes

• Microsoft.FeatureManagement.VariantDefinition.ConfigurationObject
• Microsoft.FeatureManagement.Variant.ConfigurationObject

[Степан (Stepami)]

Hey, Zhiyuan Liang (@zhiyuanliang-ms)! could you take a look please?

[Zhiyuan Liang (zhiyuanliang-ms)]

My understanding is that this enhancement is intended specifically for the custom feature definition provider scenario. Is that correct?

[Степан (Stepami)]

My understanding is that this enhancement is intended specifically for the custom feature definition provider scenario. Is that correct?

yes it is. right now i am implementing a custom provider. i need to do something like this in order to put data from an external storage into the definition:

new VariantDefinition
{
    Name = "...",
    ConfigurationValue =
        new ConfigurationBuilder()
            .AddInMemoryCollection([new("Value", variantValue.ToString())])
            .Build()
            .GetSection("Value")
}

[Степан (Stepami)]

And the idea came to me from the FeatureFilterConfiguration class