Set on the panel element's connection property before it connects (PanelConnection in app-core, restated because a panel imports only this file).
connection
PanelConnection
Readonly
Absolute or origin-relative base of /api/metrics.
/api/metrics
The snapshot stream (<apiBase>/stream).
<apiBase>/stream
Set on the panel element's
connectionproperty before it connects (PanelConnectionin app-core, restated because a panel imports only this file).