There's a set of classes in the server:

class Protocol_local;

class Ed_connection;

class Server_runnable;

class Execute_sql_statement;

created to simplify executing SQL statements from inside the server.

They are not used, and probably cannot be used anymore.

This task is to fix them, cleanup/simplify perhaps, and use them everywhere in the server where it needs to execute SQL.

This API should also be usable by plugins.

Note: often the server does not need to execute SQL, only to parse it, so these classes should allow that too.