Migrate hawkBit documentation to GitHub Pages Initial

Signed-off-by: Denislav Prinov <denislav.prinov@bosch.com>

docs/feign-client.md

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+# Feign Client
+
+In this guide we describe how to create a **Feign REST Client** based on a Spring Boot Application.
+
+---
+
+### Create Feign REST Client
+
+hawkBit provides REST interfaces for **Management API** and **DDI API**. Using these interfaces you can create a Feign client with the help of the *Feign inheritance support*.  
+Our example modules demonstrate how to create Feign client resources. Here you can find the [Management API client resources](https://github.com/eclipse-hawkbit/hawkbit/tree/master/hawkbit-mgmt-api) and the [DDI client resources](https://github.com/eclipse-hawkbit/hawkbit/tree/master/hawkbit-ddi-api).  
+A small simulator application demonstrates how you can interact with hawkBit via the [Management API](http://www.eclipse.org/hawkbit/documentation/interfaces/management-api.html).
+
+---
+
+### Example Management API Simulator
+
+In the following code section, you can see a Feign client resource example.  
+The interface extends the origin API interface to declare the `@FeignClient`.  
+The `@FeignClient` declares that a REST client with that interface should be created.
+
+This interface can be autowired and used as a normal Java interface:
+
+```java
+@FeignClient(url = "${hawkbit.url:localhost:8080}/" + MgmtRestConstants.TARGET_V1_REQUEST_MAPPING)
+public interface MgmtTargetClientResource extends MgmtTargetRestApi {
+}
+
+public class CreateStartedRolloutExample {
+
+    @Autowired
+    private MgmtTargetClientResource targetResource;
+
+    public void run() {
+
+        // create ten targets
+        targetResource.createTargets(new TargetBuilder().controllerId("00-FF-AA-0").name("00-FF-AA-0")
+                .description("Targets used for rollout example").buildAsList(10));
+    }
+}
+```
+
+Example projects:  
+- [hawkbit-example-mgmt-feign-client](https://github.com/eclipse-hawkbit/hawkbit-examples/tree/master/hawkbit-example-mgmt-feign-client)  
+- [hawkbit-example-ddi-feign-client](https://github.com/eclipse-hawkbit/hawkbit-examples/tree/master/hawkbit-example-ddi-feign-client)  
+- [hawkbit-example-mgmt-simulator](https://github.com/eclipse-hawkbit/hawkbit-examples/tree/master/hawkbit-example-mgmt-simulator)  
+
+---
+
+### Feign Client Configuration
+
+At [`hawkbit-example-core-feign-client`](https://github.com/eclipse-hawkbit/hawkbit-examples/tree/master/hawkbit-example-core-feign-client) there is a Spring configuration to auto configure some beans, which can be reused for your own Feign client:
+
+```java
+@Configuration
+@ConditionalOnClass(Feign.class)
+@Import(FeignClientsConfiguration.class)
+public class FeignClientConfiguration {
+
+    @Bean
+    public ApplicationJsonRequestHeaderInterceptor jsonHeaderInterceptor() {
+        return new ApplicationJsonRequestHeaderInterceptor();
+    }
+
+    @Bean
+    public Contract feignContract() {
+        return new IgnoreMultipleConsumersProducersSpringMvcContract();
+    }
+}
+```