Doc: Recommend using same configs on all Airflow components (#17146)

Some users seem to be using different configs for different components. This doc makes it clear on what we recommend.

Context: apache/airflow#16754 (comment)

>I'm new to Airflow and I haven't seen an explicit part within the docs that says "all configuration must be shared between airflow components". In fact, all configuration keys are prefixed with some naming scheme which led me to think that some are common, some are for webserver etc... I personally don't like to have common configuration because changing a single setting requires a change in all components (hence restart) but I get that this is intentional for Airflow. I think this can be better communicated throughout the docs.

GitOrigin-RevId: 3a263ab5b0b8b8b796d96f060e6ccd4a0e379bf3

docs/apache-airflow/configurations-ref.rst

@@ -22,6 +22,11 @@ Configuration Reference
 This page contains the list of all the available Airflow configurations that you
 can set in ``airflow.cfg`` file or using environment variables.
 
+Use the same configuration across all the Airflow components. While each component
+does not require all, some configurations need to be same otherwise they would not
+work as expected. A good example for that is :ref:`secret_key<config:webserver__secret_key>` which
+should be same on the Webserver and Worker to allow Webserver to fetch logs from Worker.
+
 .. note::
     For more information on setting the configuration, see :doc:`howto/set-config`
 

docs/apache-airflow/howto/set-config.rst

@@ -115,3 +115,9 @@ the example below.
 
 .. note::
     See :doc:`../modules_management` for details on how Python and Airflow manage modules.
+
+.. note::
+    Use the same configuration across all the Airflow components. While each component
+    does not require all, some configurations need to be same otherwise they would not
+    work as expected. A good example for that is :ref:`secret_key<config:webserver__secret_key>` which
+    should be same on the Webserver and Worker to allow Webserver to fetch logs from Worker.