DOC: add warnings for non supported external usage of TAP/TAP+
.. _astroquery.utils.tap:
+.. Warning::
+ This module is for internal astroquery use only with the purpose to
+ support the modules developed and maintained by ESA (``astroquery.gaia``,
+ ``astroquery.esasky``, and modules within ``astroquery.esa``).
+ If you need a TAP implementation, especially to access non-ESA services,
+ we recommend to use `pyVO <https://pyvo.readthedocs.io/en/latest/>`__ instead.
+ Our intention is to merge the functionalities and remove TAP/TAP+ from astroquery.
+
+
*********************************
TAP/TAP+ (`astroquery.utils.tap`)
*********************************
