Add connection methods is_connected() and ping_server() (#528)

* Replace connection handle method check_connection() with is_connected() and ping_server()

* When a connections is fetched from a pool perform a validity check which can be one of none, passive or ping.

* Add the methods is_connected() and ping_server() to the connection template class.

* Remove unused #include and add mising #include.

* Add tests for the connection methods is_connected() and ping_server().

tests/postgresql/usage/CMakeLists.txt

@@ -30,8 +30,8 @@ set(test_files
     Basic.cpp
     BasicConstConfig.cpp
     Blob.cpp
+    Connection.cpp
     ConnectionPool.cpp
-    Constructor.cpp
     Date.cpp
     DateTime.cpp
     Exceptions.cpp

tests/postgresql/usage/Connection.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2017, Serge Robyns
+ * Copyright (c) 2023, Vesselin Atanasov
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,
@@ -23,13 +24,17 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include "../../include/ConnectionTests.h"
+#include "make_test_connection.h"
+
 #include <sqlpp11/postgresql/connection.h>
 #include <sqlpp11/sqlpp11.h>
 
-namespace sql = sqlpp::postgresql;
-
-int Constructor(int, char*[])
+int Connection(int, char*[])
 {
-  sql::connection db;
+  namespace sql = sqlpp::postgresql;
+  namespace test = sqlpp::test;
+
+  test::test_normal_connection<sql::connection>(sql::make_test_config());
   return 0;
 }