fix(user fields): missing creationDate in details (#9250)

# Which Problems Are Solved

The `creationDate` property on user search V2 endpoint was missing

# How the Problems Are Solved

Added property in v2 `object.proto` and in the function creating the
details on each call

# Additional Changes
- none
# Additional Context
closes #8552

---------

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>

proto/zitadel/object/v2/object.proto

@@ -78,6 +78,8 @@ message Details {
       example: "\"69629023906488334\"";
     }
   ];
+  //creation_date is the timestamp where the first operation on the object was made
+  google.protobuf.Timestamp creation_date = 4;
 }
 
 message ListDetails {

proto/zitadel/object/v2beta/object.proto

@@ -78,6 +78,8 @@ message Details {
       example: "\"69629023906488334\"";
     }
   ];
+  //creation_date is the timestamp where the first operation on the object was made
+  google.protobuf.Timestamp creation_date = 4;
 }
 
 message ListDetails {