Run Trigger Page: Configurable number of recent configs (apache#36878)

* Run Trigger Page: Configurable number of recent configs
* no abbreviations in configuration names

airflow/config_templates/config.yml

@@ -1875,6 +1875,13 @@ webserver:
       type: boolean
       example: ~
       default: "False"
+    num_recent_configurations_for_trigger:
+      description: |
+        Number of recent DAG run configurations in the selector on the trigger web form.
+      version_added: 2.9.0
+      type: integer
+      example: "10"
+      default: "5"
     allow_raw_html_descriptions:
       description: |
         A DAG author is able to provide any raw HTML into ``doc_md`` or params description in

airflow/www/views.py

@@ -2029,6 +2029,7 @@ def trigger(self, dag_id: str, session: Session = NEW_SESSION):
             flash(f"Cannot create dagruns because the dag {dag_id} has import errors", "error")
             return redirect(origin)
 
+        num_recent_confs = conf.getint("webserver", "num_recent_configurations_for_trigger")
         recent_runs = session.execute(
             select(DagRun.conf, func.max(DagRun.run_id).label("run_id"), func.max(DagRun.execution_date))
             .where(
@@ -2038,7 +2039,7 @@ def trigger(self, dag_id: str, session: Session = NEW_SESSION):
             )
             .group_by(DagRun.conf)
             .order_by(func.max(DagRun.execution_date).desc())
-            .limit(5)
+            .limit(num_recent_confs)
         )
         recent_confs = {
             run_id: json.dumps(run_conf)