Add explicit information about how to write task logs (#30732)

There was no explicit information in our documentation on how to
write logs from your tasks. While for classic operators, that is
easy and straightforward as they all have log property which
is the right logger coming from LoggingMixin, for taskflow code
and custom classes it is is not straightforward that you have to
use `airflow.task` logger (or a child of it) or that you have
extend LoggingMixin to use the built-in logging configuration.

GitOrigin-RevId: 29bd9bf9d46bf072fec4606b0059d1bd3b85bf81

Author: potiuk

docs/apache-airflow/administration-and-deployment/logging-monitoring/logging-tasks.rst

@@ -54,6 +54,39 @@ These patterns can be adjusted by :ref:`config:logging__log_filename_template`.
 
 In addition, you can supply a remote location to store current logs and backups.
 
+Writing to task logs from your code
+-----------------------------------
+
+Most operators will write logs to the task log automatically. This is because they derive from they
+have a ``log`` logger that you can use to write to the task log.
+This logger is created and configured by :class:`~airflow.utils.log.LoggingMixin` that all classic
+operators derive from.
+
+If you want to log to the task log from a custom class of yours you can do the following:
+
+* make sure your class extends from :class:`~airflow.utils.log.LoggingMixin`
+* just use standard print statements to print to stdout
+* use the ``airflow.task`` logger that is configured by default or create logger where ``airflow.task`` is
+  the parent logger
+
+The last option is the most flexible, as you can create your own logger and configure it as you see fit
+via advanced configuration options below.
+
+Using task logger directly:
+
+.. code-block:: python
+
+  logger = logging.getLogger("airflow.task")
+  logger.info("This is a log message")
+
+Using child logger of task logger:
+
+.. code-block:: python
+
+  child_logger = logging.getLogger("airflow.task.child")
+  child_logger.info("This is a child log message")
+
+
 Interleaving of logs
 --------------------