Discord integration: no possibility to configure the webhook content object

[aZ2394]

Hi there,
According to the code of the Discord integration, there is no chance to specify Web hook content field from the message notification template. Just a embed title&message can be configured.
It's useful thing to have it when you want to tag person/role in alert. It can be doable in title&message of the embed message but user won't get a notification due to Discord API limitation.
So, it limit the tagging in Discord integration at all, and there is no chance with the current implementation to notify specific user about the alert.

What did you do?
Sent an alert to discord with the tagged user/role

What did you expect to see?
Tagged user should be notified in Discord client

What did you see instead? Under which circumstances?
Just an mention in alert without any notification for user in Discord client

• Alertmanager version:

alertmanager, version 0.26.0 (branch: HEAD, revision: d7b4f0c)
build user: root@df8d7debeef4
build date: 20230824-11:11:58
go version: go1.20.7
platform: linux/amd64
tags: netgo

• Prometheus version:

prometheus, version 2.48.1 (branch: HEAD, revision: 63894216648f0d6be310c9d16fb48293c45c9310)
build user: root@71f108ff5632
build date: 20231208-23:33:22
go version: go1.21.5
platform: linux/amd64
tags: netgo,builtinassets,stringlabels

• Alertmanager configuration file:

route:
  group_by: ['alertname', 'job']

  group_wait: 30s
  group_interval: 5m
  repeat_interval: 6h

  receiver: discord2

  routes:
      - matchers:
          - service="discord1"
        receiver: discord1
        group_interval: 12h
        repeat_interval: 24h


receivers:
- name: discord1
  discord_configs:
  - webhook_url: ''
    title: '{{ template "discord.default.title" . }}'
    message: '{{ template "discord.default.message" . }}'

- name: discord2
  discord_configs:
  - webhook_url: ''
    title: '{{ template "discord.default2.title" . }}'
    message: '{{ template "discord.default2.message" . }}'
    send_resolved: false


templates:
- '/etc/alertmanager/templates/default.tmpl'

• Prometheus configuration file:

insert configuration here (if relevant to the issue)

• Logs:

insert Prometheus and Alertmanager logs relevant to the issue here