T6934: Add preshared key for zabbix-agent monitoring service

- Allow configure preshared key for zabbix-agent
- Added op mode command for generatre random psk secret
- Removed duplicate xml definition for psk settings


Configure authentication mode:
```
# set service monitoring zabbix-agent authentication mode
Possible completions:
   pre-shared-secret    Use a pre-shared secret key
```

Configure PSK Settings:
```
# set service monitoring zabbix-agent authentication psk
Possible completions:
   id                   ID for authentication
   secret               pre-shared secret key

```

Generate Random PSK:
```
$ generate psk random
Possible completions:
  <Enter>               Execute the current command
  size                  Key size in bytes

```

1 files changed, 13 insertions, 0 deletions

diff --git a/data/templates/zabbix-agent/zabbix-agent.conf.j2 b/data/templates/zabbix-agent/zabbix-agent.conf.j2
index e6dcef872..b8df2d177 100644
--- a/data/templates/zabbix-agent/zabbix-agent.conf.j2
+++ b/data/templates/zabbix-agent/zabbix-agent.conf.j2
@@ -75,3 +75,16 @@ Include={{ directory }}/*.conf
 Timeout={{ timeout }}
 {% endif %}
 
+{% if authentication is vyos_defined and authentication.mode is vyos_defined %}
+{%     if authentication.mode == "pre-shared-secret" %}
+TLSConnect=psk
+TLSAccept=psk
+{%     endif %}
+{%     if authentication.psk.secret is vyos_defined %}
+TLSPSKFile={{ service_psk_file }}
+{%     endif %}
+{%     if authentication.psk.id is vyos_defined %}
+TLSPSKIdentity={{ authentication.psk.id }}
+{%     endif %}
+{% endif %}
+