[JIRA_CONFIG] Template fields alert manager --> jira integration does not work

[vmkullo]

Hellow!
Tried to use a new feature that allows to integrate Alertmanager with Jira without using jiralert https://github.com/prometheus/alertmanager/blob/main/docs/configuration.md#jira_config.
Encountered a problem that the “template” in “fields” is not readable, this is what my configuration file block looks like:

fields:
customfield_10002: "AB-123"
customfield_11314: [ { "key": "ABCD-123" } ]
customfield_11315: [ { "key": "ABCD-123" } ]
customfield_13707: '{{ template "jira.test.alertname" . }}'
customfield_13708: '{{ template "jira.test.namespace" . }}'
customfield_13709: '{{ template "jira.test.instance" . }}'

As a result when trying to send a notification, the sending happens, but the values are not read out and we get template names in the notification text, for example :
'alertname = {{ template 'jira.test.alertname' . }}'
namespace = {{ template “jira.test.namespace” . }}

And I want to get:
alertname = prod-123 (example)
namespace = monitoring (example)

Can you tell me if Alertmanager can't handle template in fields correctly or is there another construct for this?