[mod] engines: migrate to setup() from init() for simple tasks

searx/engines/mysql_server.py

@@ -25,6 +25,8 @@ Implementations
 
 """
 
+import typing as t
+
 from searx.result_types import EngineResults
 
 try:
@@ -60,15 +62,17 @@ paging = True
 _connection = None
 
 
-def init(engine_settings):
-    global _connection  # pylint: disable=global-statement
-
+def setup(engine_settings: dict[str, t.Any]) -> bool | None:
     if 'query_str' not in engine_settings:
         raise ValueError('query_str cannot be empty')
 
     if not engine_settings['query_str'].lower().startswith('select '):
         raise ValueError('only SELECT query is supported')
 
+
+def init(_):
+    global _connection  # pylint: disable=global-statement
+
     _connection = mysql.connector.connect(
         database=database,
         user=username,