OpenFeature integration

<dependency>
  <groupId>dev.westyx.nexus</groupId>
  <artifactId>nexus-spring-boot-starter</artifactId>
  <version>0.10.0</version>
</dependency>
<dependency>
  <groupId>dev.westyx.nexus</groupId>
  <artifactId>nexus-openfeature-spring-boot</artifactId>
  <version>0.10.0</version>
</dependency>

implementation("dev.westyx.nexus:nexus-spring-boot-starter:0.10.0")
implementation("dev.westyx.nexus:nexus-openfeature-spring-boot:0.10.0")

import dev.openfeature.sdk.OpenFeatureAPI;
import dev.westyx.nexus.openfeature.NexusProvider;

@PostConstruct
void configureOpenFeature() {
    OpenFeatureAPI.getInstance().setProvider(new NexusProvider(nexusClient));
}

Client ofClient = OpenFeatureAPI.getInstance().getClient("my-service");
MutableContext ctx = new MutableContext();

boolean darkMode  = ofClient.getBooleanValue("dark-mode", false, ctx);
String  apiUrl    = ofClient.getStringValue("api.base-url", "https://default.example.com", ctx);
double  rateLimit = ofClient.getDoubleValue("rate-limit", 100.0, ctx);
int     maxItems  = ofClient.getIntegerValue("max-items", 50, ctx);