Fix mssql concurrent insert id

The implementation of db_insert_id() in mssql relied on IDENT_CURRENT
making it not thread safe.
Modify it to use ADOdb native implementation, based on SCOPE_IDENTITY()
which is session independent.

Fixes: #25442

core/database_api.php

@@ -451,32 +451,41 @@ function db_result( $p_result, $p_row_index = 0, $p_col_index = 0 ) {
 }
 
 /**
- * return the last inserted id for a specific database table
+ * Return the last inserted ID after a insert statement.
+ * Warning: this function must be used immediately after the insert statement
+ *
+ * This relies on ADOdb to get the entity id when this functionality is available
+ * for the specific driver, and it makes sense in our model.
+ * Natively supported:
+ * - mysqli, using: mysqli_insert_id(connection).
+ * - mssqlnative, using SCOPE_IDENTITY().
+ * Not natively supported:
+ * - pgsql, oracle, using the underlying sequence for the table.
+ *
+ * Since the table is needed for those drivers where a sequence is used, the
+ * $p_table parameter is mandatory to ensure portability.
+ * Warning: $p_table is not expected to be a different table than the one used
+ * for the previous insert. Note that it's not even used by some drivers.
+ *
  * @param string $p_table A valid database table name.
  * @param string $p_field A valid field name (default 'id').
  * @return integer last successful insert id
  */
-function db_insert_id( $p_table = null, $p_field = 'id' ) {
+function db_insert_id( $p_table, $p_field = 'id' ) {
 	global $g_db, $g_db_functional_type;
 
-	if( isset( $p_table ) ) {
-		switch( $g_db_functional_type ) {
+	switch( $g_db_functional_type ) {
 			case DB_TYPE_ORACLE:
 				$t_query = 'SELECT seq_' . $p_table . '.CURRVAL FROM DUAL';
 				break;
 			case DB_TYPE_PGSQL:
 				$t_query = 'SELECT currval(\'' . $p_table . '_' . $p_field . '_seq\')';
 				break;
-			case DB_TYPE_MSSQL:
-				$t_query = 'SELECT IDENT_CURRENT(\'' . $p_table . '\')';
-				break;
-		}
-		if( isset( $t_query ) ) {
-			$t_result = db_query( $t_query );
-			return (int)db_result( $t_result );
-		}
+			default:
+				return $g_db->Insert_ID();
 	}
-	return $g_db->Insert_ID();
+	$t_result = db_query( $t_query );
+	return (int)db_result( $t_result );
 }
 
 /**