implemented support for GET /_admin/server/id

Author: rashtao

src/main/java/com/arangodb/ArangoDB.java

@@ -762,6 +762,16 @@ public synchronized ArangoDB build() {
      */
     ServerRole getRole() throws ArangoDBException;
 
+    /**
+     * Returns the id of a server in a cluster.
+     *
+     * @return the server id
+     * @throws ArangoDBException
+     * @see <a href="https://www.arangodb.com/docs/stable/http/administration-and-monitoring.html#return-id-of-a-server-in-a-cluster">API
+     * Documentation</a>
+     */
+    String getServerId() throws ArangoDBException;
+
     /**
      * Create a new user. This user will not have access to any database. You need permission to the _system database in
      * order to execute this call.

src/main/java/com/arangodb/internal/ArangoDBImpl.java

@@ -174,6 +174,11 @@ public ServerRole getRole() throws ArangoDBException {
         return executor.execute(getRoleRequest(), getRoleResponseDeserializer());
     }
 
+    @Override
+    public String getServerId() throws ArangoDBException {
+        return executor.execute(getServerIdRequest(), getServerIdResponseDeserializer());
+    }
+
     @Override
     public UserEntity createUser(final String user, final String passwd) throws ArangoDBException {
         return executor.execute(createUserRequest(db().name(), user, passwd, new UserCreateOptions()),

src/main/java/com/arangodb/internal/InternalArangoDB.java

@@ -47,6 +47,7 @@ public abstract class InternalArangoDB<E extends ArangoExecutor> extends ArangoE
     private static final String PATH_API_ADMIN_LOG_ENTRIES = "/_admin/log/entries";
     private static final String PATH_API_ADMIN_LOG_LEVEL = "/_admin/log/level";
     private static final String PATH_API_ROLE = "/_admin/server/role";
+    private static final String PATH_API_SERVER_ID = "/_admin/server/id";
     private static final String PATH_ENDPOINTS = "/_api/cluster/endpoints";
     private static final String PATH_API_USER = "/_api/user";
 
@@ -58,10 +59,18 @@ protected Request getRoleRequest() {
         return request(ArangoRequestParam.SYSTEM, RequestType.GET, PATH_API_ROLE);
     }
 
+    protected Request getServerIdRequest() {
+        return request(ArangoRequestParam.SYSTEM, RequestType.GET, PATH_API_SERVER_ID);
+    }
+
     protected ResponseDeserializer<ServerRole> getRoleResponseDeserializer() {
         return response -> util().deserialize(response.getBody().get("role"), ServerRole.class);
     }
 
+    protected ResponseDeserializer<String> getServerIdResponseDeserializer() {
+        return response -> util().deserialize(response.getBody().get("id"), String.class);
+    }
+
     protected Request createDatabaseRequest(final DBCreateOptions options) {
         final Request request = request(ArangoRequestParam.SYSTEM, RequestType.POST,
                 InternalArangoDatabase.PATH_API_DATABASE);