[mod] remove option ui.static_use_hash (cache busting) (#5004)

Cache busting has caused serious problems for users in the past, here are two
examples:

- https://github.com/searxng/searxng/issues/4419
- https://github.com/searxng/searxng/issues/4481

And it makes development and deployment significantly more complex because it
binds the client side to the server side:

- https://github.com/searxng/searxng/pull/4466

In the light of a decoupled development of the WEB clients from the server side:

- https://github.com/searxng/searxng/pull/4988

is it appropriate to abandon this feature. In fact,  it has been ineffective
since #4436 anyway.

However, the benefit has always been questionable, since at best only a few kB
of data are saved (at least in the context of an image_proxy, the effect is below
the detection limit). Ultimately, the client is responsible for caching.

Related: https://github.com/searxng/searxng/issues?q=label%3A%22clear%20browser%20cache%22

Closes: https://github.com/searxng/searxng/pull/4466
Closes: https://github.com/searxng/searxng/issues/1326
Closes: https://github.com/searxng/searxng/issues/964

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

docs/admin/architecture.rst

@@ -29,8 +29,8 @@ up and maintained by the scripts from our :ref:`toolboxing`.
 
    Reference architecture of a public SearXNG setup.
 
-The reference installation activates ``server.limiter``, ``server.image_proxy``
-and ``ui.static_use_hash`` (:origin:`/etc/searxng/settings.yml
+The reference installation activates ``server.limiter`` and
+``server.image_proxy`` (:origin:`/etc/searxng/settings.yml
 <utils/templates/etc/searxng/settings.yml>`)
 
 .. literalinclude:: ../../utils/templates/etc/searxng/settings.yml

docs/admin/installation-searxng.rst

@@ -86,7 +86,6 @@ below. This setup:
 
 - enables :ref:`limiter <limiter>` to protect against bots
 - enables :ref:`image proxy <image_proxy>` for better privacy
-- enables :ref:`cache busting <static_use_hash>` to save bandwidth
 
 Modify the ``/etc/searxng/settings.yml`` to your needs:
 
@@ -129,4 +128,3 @@ configuration file.
 If everything works fine, hit ``[CTRL-C]`` to stop the *webapp* and disable the
 debug option in ``settings.yml``. You can now exit SearXNG user bash session (enter exit
 command twice).  At this point SearXNG is not demonized; uwsgi allows this.
-

docs/admin/installation-uwsgi.rst

@@ -181,10 +181,7 @@ uWSGI setup
 
 Create the configuration ini-file according to your distribution and restart the
 uwsgi application.  As shown below, the :ref:`installation scripts` installs by
-default:
-
-- a uWSGI setup that listens on a socket and
-- enables :ref:`cache busting <static_use_hash>`.
+default a uWSGI setup that listens on a socket.
 
 .. tabs::
 

docs/admin/settings/settings_ui.rst

@@ -10,7 +10,6 @@
 .. code:: yaml
 
    ui:
-     static_use_hash: false
      default_locale: ""
      query_in_title: false
      infinite_scroll: false
@@ -23,11 +22,6 @@
      hotkeys: default
      url_formatting: pretty
 
-.. _static_use_hash:
-
-``static_use_hash`` : ``$SEARXNG_STATIC_USE_HASH``
-  Enables `cache busting`_ of static files.
-
 ``default_locale`` :
   SearXNG interface language.  If blank, the locale is detected by using the
   browser language.  If it doesn't work, or you are deploying a language

docs/admin/update-searxng.rst

@@ -58,10 +58,6 @@ and then, to name just a few:
 - Bot protection has been switched from filtron to SearXNG's :ref:`limiter
   <limiter>`, this requires a :ref:`Valkey <settings valkey>` database.
 
-- To save bandwidth :ref:`cache busting <static_use_hash>` has been implemented.
-  To get in use, the ``static-expires`` needs to be set in the :ref:`uwsgi
-  setup`.
-
 To stay tuned and get in use of the new features, instance maintainers have to
 update the SearXNG code regularly (see :ref:`update searxng`).  As the above
 examples show, this is not always enough, sometimes services have to be set up