Added functionality to automatically ingest custom airflow.cfg file u…

…pon startup and the associated documentation

docs/apache-airflow/howto/docker-compose/docker-compose.yaml

@@ -61,6 +61,7 @@ x-airflow-common:
     AIRFLOW__CORE__DAGS_ARE_PAUSED_AT_CREATION: 'true'
     AIRFLOW__CORE__LOAD_EXAMPLES: 'true'
     AIRFLOW__API__AUTH_BACKENDS: 'airflow.api.auth.backend.basic_auth,airflow.api.auth.backend.session'
+    TEST: 
     # yamllint disable rule:line-length
     # Use simple http server on scheduler for health checks
     # See https://airflow.apache.org/docs/apache-airflow/stable/administration-and-deployment/logging-monitoring/check-health.html#scheduler-health-check-server
@@ -74,6 +75,10 @@ x-airflow-common:
     - ${AIRFLOW_PROJ_DIR:-.}/logs:/opt/airflow/logs
     - ${AIRFLOW_PROJ_DIR:-.}/config:/opt/airflow/config
     - ${AIRFLOW_PROJ_DIR:-.}/plugins:/opt/airflow/plugins
+    #The following line can be used to use a custom airflow.cfg, stored in the AIRFLOW_PROJ_DIR
+    #Uncomment the following line to make use of this
+    #- ${AIRFLOW_PROJ_DIR:-.}/airflow.cfg:/opt/airflow/airflow.cfg
+
   user: "${AIRFLOW_UID:-50000}:0"
   depends_on:
     &airflow-common-depends-on

docs/apache-airflow/howto/docker-compose/index.rst

@@ -340,6 +340,16 @@ that conflicts with the version of apache-airflow that you are using.
 Run ``docker compose build`` to build the image, or add ``--build`` flag to ``docker compose up`` or
 ``docker compose run`` commands to build the image automatically as needed.
 
+Special case - Adding a custom config file
+==========================================
+
+If you have a custom config file and wish to use it in your Airflow instance, you need to perform the following steps:
+
+1) Remove comment from the ``- ${AIRFLOW_PROJ_DIR:-.}/airflow.cfg:/opt/airflow/airflow.cfg`` line 
+   in the ``docker-compose.yaml`` file.  
+
+2) Place your custom ``airflow.cfg`` file in the same folder as the ``docker-compose.yaml`` file.
+
 Networking
 ==========