GB-23 GB-24 Networking with the GBFeaturesRepository

[tinahollygb]

Adds networking via the new GBFeaturesRepository class, allowing developers to fetch both unencrypted and encrypted features.

An instance of this class can be created with an endpoint URL, TTL (seconds), and optional encryption key for decrypting encrypted payloads.

Features

• Configure the refresh rate with ttlSeconds (defaults to 60)
• gbFeaturesRepository.initialize() makes the network request to the GrowthBook SDK endpoint to get the features, and caches the response in-memory.
• gbFeaturesRepository.getFeaturesJson() allows you to get the features JSON as a string, which simplifies the implementation of fetching and initializing a GBContext.
• Appends the client and version number to the User-Agent header when fetching features, e.g. growthbook-sdk-java/0.3.0
• Adds the ability to subscribe to a callback when features are refreshed with onFeaturesRefresh(FeatureRefreshCallback callback)

Issues

• Closes https://linear.app/growthbook/issue/GB-23
• Closes https://linear.app/growthbook/issue/GB-24

[linear[bot]]

GB-23 [Java SDK]: Implement feature repository that fetches and caches features in-memory

Initial `GBFeatureRepository` class. # Acceptance Criteria * ✅ should fetch features with provided endpoint and optional encryptionKey config. * ✅ expose method `getFeaturesJson()` * ✅ should send a user agent string to identify itself as the Java SDK with version

GB-24 [Java SDK]: Add caching with configurable TTL to the feature repository

The existing `GBFeatureRepository` class should be: * ✅ Configurable TTL for the caching * ✅ Have functionality to refresh the features when the cache has expired * ✅ Support a list of callbacks to allow implementations to listen for feature updates.