Feature Flags Compact Offline Framework

[android10]

This PR aims to Introduce a first version, which will let to define Feature Flags at compile time.

API Usage:

        Flag.ExampleFeature whenActivated {
            doSomething()
        } otherwise {
            //do something else
        }

Flags are defined at compile time per Product Flavor:

File: FeatureFlags.kt

/**
 * Defines a map for activated flags per product flavor.
 */
object FeatureFlags {
    val activated = mapOf(

        //Enabled Features for DEV Product Flavor
        ProductFlavors.DEV to setOf(
            Features.FEATURE_HELLO,
            Features.FEATURE_BYE),

        //Enabled Features for INTERNAL Product Flavor
        ProductFlavors.INTERNAL to setOf(
            Features.FEATURE_BYE),

        //Enabled Features for PUBLIC Product Flavor
        ProductFlavors.PUBLIC to setOf(
            Features.FEATURE_HELLO))

Compile time flags values should be assigned to Flag class for usage at code level:

/**
 * Feature flags states (activated/deactivated) can be used as conditionals.
 *
 * ### Example:
 *
 * ```Flag.Conversations whenActivated { fn } otherwise { fn }```
 */
internal sealed class Flag(enabled: Boolean) : FeatureFlag(enabled) {

    /**
     * Defined Feature Flags.
     * @see "FeatureFlags.kt" file for compile-time feature definition.
     */
    object Search : Flag(BuildConfig.FEATURE_HELLO)
    object Conversations : Flag(BuildConfig.FEATURE_BYE)
}