Resolve GAIAXAUTH-20

Closes GAIAXAUTH-20

service/src/main/java/eu/gaiax/difs/aas/client/IamClient.java

+package eu.gaiax.difs.aas.client;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.client.WebClient;
+import reactor.core.publisher.Flux;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@Component
+public class IamClient {
+
+    private final WebClient client;
+    private static final ParameterizedTypeReference<Map<String, Object>> MAP_TYPE_REF = new ParameterizedTypeReference<>() {
+    };
+
+    @Value("${aas.iam.base-uri}")
+    private String baseUri;
+    @Value("${aas.iam.client-registration-uri}")
+    private String clientRegistrationUri;
+    @Value("${aas.iam.client-secret}")
+    private String clientSecret;
+
+    public IamClient() {
+        client = WebClient.builder()
+                .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
+                .build();
+        }
+
+    public Map<String, Object> registerIam(String clientName, List<String> redirectUris) {
+
+        Map<String, Object> map = new HashMap<>();
+        map.put("client_name", clientName);
+        map.put("redirect_uris", redirectUris);
+        map.put("grant_types", List.of("authorization_code"));
+
+        Flux<Map<String, Object>> trustServiceResponse = client.post()
+                .uri(baseUri+clientRegistrationUri)
+                .headers(h -> h.setBearerAuth(clientSecret))
+                .accept(MediaType.APPLICATION_JSON)
+                .bodyValue(map)
+                .retrieve()
+                .bodyToFlux(MAP_TYPE_REF);
+
+        return trustServiceResponse.blockFirst();
+    }
+}