The text and links in the header configurations were always the root
elements that were editable. For them to be properly editable, we need
their container (at minimum) to be the root editable element. Indeed,
on root editable elements, only the class and style can be changed (if
not dynamic). But changing a link requires to change the href, the
target. Changing a text style requires to change the tag entirely, etc.
For this to work, the `_link_class` configuration was removed, it was in
fact mostly useless and actually even breaking some layouts. So doing
this fix actually improves the design as well. For the layout were it
made sense, it actually became useless by refactoring the templates.
This was necessary anyway for texts which did not use `_link_class` but
were root editable nodes anyway because of the `t-if` conditions laying
around.
closesodoo/odoo#140869
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>