Improve entity constructors

entity/src/main/java/org/mercury_im/messenger/entity/IAccount.java

@@ -12,7 +12,11 @@ public class IAccount implements Account {
     protected boolean enabled;
 
     public IAccount() {
-        this.id = UUID.randomUUID();
+        this(UUID.randomUUID());
+    }
+
+    public IAccount(UUID id) {
+        this.id = id;
     }
 
     @Override

entity/src/main/java/org/mercury_im/messenger/entity/chat/IDirectChat.java

@@ -13,7 +13,11 @@ public class IDirectChat implements DirectChat {
     protected ChatPreferences preferences;
 
     public IDirectChat() {
-        this.id = UUID.randomUUID();
+        this(UUID.randomUUID());
+    }
+
+    public IDirectChat(UUID id) {
+        this.id = id;
     }
 
     @Override

entity/src/main/java/org/mercury_im/messenger/entity/chat/IGroupChat.java

@@ -16,7 +16,11 @@ public class IGroupChat implements GroupChat {
     protected Set<Peer> participants;
 
     public IGroupChat() {
-        this.id = UUID.randomUUID();
+        this(UUID.randomUUID());
+    }
+
+    public IGroupChat(UUID id) {
+        this.id = id;
     }
 
     @Override

entity/src/main/java/org/mercury_im/messenger/entity/contact/IPeer.java

@@ -15,7 +15,11 @@ public class IPeer implements Peer {
     protected boolean approved;
 
     public IPeer() {
-        this.id = UUID.randomUUID();
+        this(UUID.randomUUID());
+    }
+
+    public IPeer(UUID id) {
+        this.id = id;
     }
 
     @Override

entity/src/main/java/org/mercury_im/messenger/entity/message/IMessage.java

@@ -15,6 +15,13 @@ public class IMessage implements Message {
     protected MessageMetadata metadata;
     protected MessageDirection direction;
 
+    public IMessage() {
+        this(UUID.randomUUID());
+    }
+
+    public IMessage(UUID id) {
+        this.id = id;
+    }
 
     @Override
     public UUID getId() {