Access filter defaults to public

[sergiimk]

Changed:

• Not specifying a filter defaults to ["public"] for extra safety

TODO:
In global search and activity APIs I think byAccessLevels is not enough - we need an ability to specify something like:

WHERE
access_level IN [<default levels>]
OR (project_id = A AND access_level IN [<project_a_levels>])
OR (project_id = B AND access_level IN [<project_b_levels>])
...