Remove conf from Task Context

This was initially added in response to #168. However, we now have `ti.log_url` that is used for that; example usages:

https://github.com/apache/airflow/blob/dcd41f60f1c9b5583b49bfb49b6d85c640a2892c/airflow/models/taskinstance.py#L1362

https://github.com/apache/airflow/blob/dcd41f60f1c9b5583b49bfb49b6d85c640a2892c/providers/src/airflow/providers/smtp/notifications/templates/email.html#L28

https://github.com/apache/airflow/blob/dcd41f60f1c9b5583b49bfb49b6d85c640a2892c/docs/apache-airflow/howto/email-config.rst?plain=1#L76

So, to simplify what we need to pass from API server to the Task SDK, I want to simplify and remove things that aren't needed. In this case, this is good so we don't pass/expore secrets unnecesarily via `conf`

Author: kaxil

airflow/models/taskinstance.py

@@ -1010,7 +1010,6 @@ def get_triggering_events() -> dict[str, list[AssetEvent]]:
     # * KNOWN_CONTEXT_KEYS in airflow/utils/context.py
     # * Table in docs/apache-airflow/templates-ref.rst
     context: dict[str, Any] = {
-        "conf": conf,
         "dag": dag,
         "dag_run": dag_run,
         "data_interval_end": timezone.coerce_datetime(data_interval.end),

airflow/utils/context.py

@@ -67,7 +67,6 @@
 # * Context in airflow/utils/context.pyi.
 # * Table in docs/apache-airflow/templates-ref.rst
 KNOWN_CONTEXT_KEYS: set[str] = {
-    "conf",
     "conn",
     "dag",
     "dag_run",

airflow/utils/context.pyi

@@ -32,7 +32,6 @@ from typing import Any, overload
 from pendulum import DateTime
 from sqlalchemy.orm import Session
 
-from airflow.configuration import AirflowConfigParser
 from airflow.models.asset import AssetEvent
 from airflow.models.baseoperator import BaseOperator
 from airflow.models.dag import DAG
@@ -100,7 +99,6 @@ class InletEventsAccessors(Mapping[Asset | AssetAlias, InletEventsAccessor]):
 # * KNOWN_CONTEXT_KEYS in airflow/utils/context.py
 # * Table in docs/apache-airflow/templates-ref.rst
 class Context(TypedDict, total=False):
-    conf: AirflowConfigParser
     conn: Any
     dag: DAG
     dag_run: DagRun | DagRunPydantic

docs/apache-airflow/templates-ref.rst

@@ -79,8 +79,6 @@ Variable                                    Type                  Description
 ``{{ conn }}``                                                    Airflow connections. See `Airflow Connections in Templates`_ below.
 ``{{ task_instance_key_str }}``             str                   | A unique, human-readable key to the task instance. The format is
                                                                   | ``{dag_id}__{task_id}__{ds_nodash}``.
-``{{ conf }}``                              AirflowConfigParser   | The full configuration object representing the content of your
-                                                                  | ``airflow.cfg``. See :mod:`airflow.configuration.conf`.
 ``{{ run_id }}``                            str                   The currently running :class:`~airflow.models.dagrun.DagRun` run ID.
 ``{{ dag_run }}``                           DagRun                The currently running :class:`~airflow.models.dagrun.DagRun`.
 ``{{ test_mode }}``                         bool                  Whether the task instance was run by the ``airflow test`` CLI.

newsfragments/44820.significant.rst

@@ -0,0 +1,38 @@
+Removed ``conf`` from the Task template context
+
+The ``conf`` variable, which provided access to the full Airflow configuration (``airflow.cfg``), has been
+removed from the Task (Jinja2) template context for security and simplicity. If you
+need specific configuration values in your tasks, retrieve them explicitly in your DAG or task code
+using the ``airflow.configuration.conf`` module.
+
+For users retrieving the webserver URL (e.g., to include log links in task or callbacks), one of the
+most common use-case, use the ``ti.log_url`` property available in the ``TaskInstance`` context instead.
+
+Example:
+
+.. code-block:: python
+
+        PythonOperator(
+            task_id="my_task",
+            python_callable=my_task_callable,
+            on_failure_callback=SmtpNotifier(
+                from_email="[email protected]",
+                to="[email protected]",
+                subject="Task {{ ti.task_id }} failed",
+                html_content="Task <b>{{ ti.task_id }}</b> failed. Log URL: {{ ti.log_url }}",
+            ),
+        )
+
+* Types of change
+
+  * [x] DAG changes
+  * [ ] Config changes
+  * [ ] API changes
+  * [ ] CLI changes
+  * [ ] Behaviour changes
+  * [ ] Plugin changes
+  * [ ] Dependency changes
+
+* Migration rules needed
+
+  * Remove context key ``conf``