[doc] improve admin-docs about result proxy (morty) configuration

[1] https://github.com/searx/searx/pull/1872#issuecomment-768107138

Suggested-by @dalf [1]
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

docs/admin/installation-apache.rst

@@ -180,10 +180,6 @@ modules and create a `Location`_ configuration for the searx site.  In most
 distributions you have to un-comment the lines in the main configuration file,
 except in :ref:`The Debian Layout`.
 
-To pass the HTTP HOST header 
-With ProxyPreserveHost_ the incoming Host HTTP request header is passed to the
-proxied host.
-
 .. tabs::
 
    .. group-tab:: Ubuntu / debian
@@ -231,6 +227,11 @@ proxied host.
          LoadModule proxy_module modules/mod_proxy.so
          LoadModule proxy_http_module modules/mod_proxy_http.so
 
+With ProxyPreserveHost_ the incoming Host HTTP request header is passed to the
+proxied host.
+
+.. _apache searx via filtron plus morty:
+
 .. tabs::
 
    .. group-tab:: searx via filtron plus morty
@@ -285,15 +286,15 @@ proxied host.
 
          </Location>
 
-      Note that reverse proxy advised to be used in case of single-user or
+      For a fully result proxification add :ref:`morty's <searx morty>` **public
-      low-traffic instances.  For a fully result proxification add :ref:`morty's
+      URL** to your :origin:`searx/settings.yml`:
-      <searx morty>` **public URL** to your :origin:`searx/settings.yml`:
 
       .. code:: yaml
 
          result_proxy:
              # replace example.org with your server's public name
              url : https://example.org/morty
+             key : !!binary "insert_your_morty_proxy_key_here"
 
          server:
              image_proxy : True

docs/admin/installation-nginx.rst

@@ -163,6 +163,8 @@ Started wiki`_ is always a good resource *to keep in the pocket*.
       Create configuration at ``/etc/nginx/conf.d/searx`` and place a
       symlink to sites-enabled:
 
+.. _nginx searx via filtron plus morty:
+
 .. tabs::
 
    .. group-tab:: searx via filtron plus morty
@@ -210,15 +212,15 @@ Started wiki`_ is always a good resource *to keep in the pocket*.
              proxy_set_header   X-Scheme         $scheme;
          }
 
-      Note that reverse proxy advised to be used in case of single-user or
+      For a fully result proxification add :ref:`morty's <searx morty>` **public
-      low-traffic instances.  For a fully result proxification add :ref:`morty's
+      URL** to your :origin:`searx/settings.yml`:
-      <searx morty>` **public URL** to your :origin:`searx/settings.yml`:
 
       .. code:: yaml
 
          result_proxy:
              # replace example.org with your server's public name
              url : https://example.org/morty
+             key : !!binary "insert_your_morty_proxy_key_here"
 
          server:
              image_proxy : True

docs/admin/morty.rst

@@ -16,15 +16,22 @@ By default searx can only act as an image proxy for result images, but it is
 possible to proxify all the result URLs with an external service, morty_.
 
 To use this feature, morty has to be installed and activated in searx's
-``settings.yml``.
+``settings.yml``.  Add the following snippet to your ``settings.yml`` and
-
+restart searx:
-Add the following snippet to your ``settings.yml`` and restart searx:
 
 .. code:: yaml
 
     result_proxy:
         url : http://127.0.0.1:3000/
-        key : your_morty_proxy_key
+        key : !!binary "insert_your_morty_proxy_key_here"
+
+Note that the example above (``http://127.0.0.1:3000``) is only for single-user
+instances without a HTTP proxy.  If your morty service is public, the url is the
+address of the reverse proxy (e.g ``https://example.org/morty``).
+
+For more information about *result proxy* have a look at *"searx via filtron
+plus morty"* in the :ref:`nginx <nginx searx via filtron plus morty>` and
+:ref:`apache <apache searx via filtron plus morty>` sections.
 
 ``url``
   Is the address of the running morty service.