Cannot send notification with Signal-REST to Signal group chat

[Sohonin]

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I've found a bug and checked that ...

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• ... there are no open or closed issues that are related to my problem

Description

I would like to get notifications about the updates through Signal to a group chat. The signal-cli is able to do that if you put the group ID into the recipients. I can send messages directly with signal-cli and DIUN notifications work if a phone number is in the recipients.
Maybe the problem is that the group ID is base64 formatted and contains numbers and letters (both lower and uppercase)?
My relevant dockerfile part:

- DIUN_NOTIF_SIGNALREST_ENDPOINT=http://<containerip>:8080/v2/send
- DIUN_NOTIF_SIGNALREST_NUMBER=<phonenumber>
- DIUN_NOTIF_SIGNALREST_RECIPIENTS=["<groupid>"]
- DIUN_NOTIF_SIGNALREST_TIMEOUT=10s
- DIUN_NOTIF_SIGNALREST_TEMPLATEBODY=Docker tag {{ .Entry.Image }} has been released.

- DIUN_NOTIF_SIGNALREST_RECIPIENTS_<KEY> is not working, inserting any number into key breaks the notifications. See #1005

Expected behaviour

To get notification in a Signal group.

Actual behaviour

No message is sent.

Steps to reproduce

1. Get the group ID you want to use: http://<containerip>:8080/v1/groups/<phonenumber>
2. The group ID will be something like this: "group.<base64>"
3. In the DIUN configuration, change the recipients to the group ID (containing group.)

Diun version

v4.26.0

Docker info

Client: Docker Engine - Community
 Version:    24.0.7
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.11.2
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.21.0
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 6
  Running: 6
  Paused: 0
  Stopped: 0
 Images: 11
 Server Version: 24.0.7
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc io.containerd.runc.v2
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 3dd1e886e55dd695541fdcd67420c2888645a495
 runc version: v1.1.10-0-g18a0cb0
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.1.0-0.deb11.11-amd64
 Operating System: Debian GNU/Linux 11 (bullseye)
 OSType: linux
 Architecture: x86_64
 CPUs: 4
 Total Memory: 15.43GiB
 Name: homenas
 ID: 26d1703d-aa28-4928-ac91-07f568ceedc5
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Docker Compose config

No response

Logs

It was too long, you can find it here:
https://gist.github.com/Canibel/797b24aa2071c2c5e39e62b7ddaf49a5

Additional info

No response

[crazy-max]

cc @MrRagga-

[MrRagga-]

I do have a setup, where I also have a group configured (not a real group id):

    recipients:
      - "group.bklCDemZNzMll1PXFyHGLySLIE0SlV1VWBsQmNCbUFNMZYrc0F1UDA9RP0="

and it works perfectly fine for me.
Do you get any error message? @Sohonin