Store group info in json

src/main/java/cli/GroupInfo.java

@@ -0,0 +1,28 @@
+package cli;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+public class GroupInfo {
+    @JsonProperty
+    public final byte[] groupId;
+
+    @JsonProperty
+    public String name;
+
+    @JsonProperty
+    public List<String> members = new ArrayList<>();
+
+    @JsonProperty
+    public long avatarId;
+
+    public GroupInfo(@JsonProperty("groupId") byte[] groupId, @JsonProperty("name") String name, @JsonProperty("members") Collection<String> members, @JsonProperty("avatarId") long avatarId) {
+        this.groupId = groupId;
+        this.name = name;
+        this.members.addAll(members);
+        this.avatarId = avatarId;
+    }
+}