Support UTF-8 format for Cortex Alert manager label matchers

[rakheshkumbi]

Is your feature request related to a problem? Please describe.
For the "Add notification policy" page, it will always report error validating Alertmanager config: bad matcher format: "a"="b" when I try to any matching labels (I am using cortex alertmanager here), but it works if use the REST API of cortex.

cortex REST API:
curl -i -H "Authorization: Bearer $(TOKEN)" -H 'Content-Type: application/yaml' -X POST --data-binary @alerts.yaml $(ALERT_URL)/api/v2/alerts
alerts.yaml :

alertmanager_config: |

route:
- continue: false
matchers:
- a=b
mute_time_intervals: []
receiver: simin_contact_point
routes: []

Describe the solution you'd like
Currently the cortex doesn't support UTF-8 format for label matchers. If cortex can support the UTF-8 format for the label matcher, the issue can be resolved.

Describe alternatives you've considered
NA

Additional context
It should be possible to add any existing or not-existing matching labels in Add notification policy" page of grafana without error

[yeya24]

Currently the cortex doesn't support UTF-8 format for label matchers. If cortex can support the UTF-8 format for the label matcher, the issue can be resolved.

IIUC, this is only supported by Alertmanager together with Prometheus 3.0 upgrade?
Prometheus 3.0 compatibilty is definitely on our radar. UTF-8 support is also part of it