fix ``call_service`` API and add test service API
``call_service`` was taking a session argument. But Service is an AppoObject and
already has the same session accessible as ``self._cw``.
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^doc/book/en/apidoc$
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.*/data/database/.*\.sqlite
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^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/