[hooks/syncschema] Turn DropColumnOp into a data operation
While writing a test for a migration issue where "NOT NULL" was added to
an inlined relation column, I ran into a case where the same column was
deleted twice, which of course results in an error. This is because the
"ecrit_par" relation used by the test is ambiguous. I've hence turned
the DropColumnOp into a data operation to ensure we'll delete the column
only once in such case.
Related to #6211101
Once you have read the `RQL tutorial`_ and you know the application'`schema`_,
you're ready to define your own views. Just type the RQL query retreiving data
you're interested in in the search field. If the view used to display them
doesn't fit your need, choose another one in the possible views box (this box
isn't displayed by default, but you can activate it in your `user
preferences`_). Once you're satified, add a `bookmark`_ if you want to reuse
this view later.
.. _`RQL tutorial`: tut_rql
.. _`schema`: ../schema
.. _`user preferences`: ../myprefs
.. _`bookmark`: bookmarks
Below are some example of what can be acheived...
.. winclude:: custom_view_last_update
.. winclude:: custom_view_rss