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, 28 insertions, 0 deletions

diff --git a/op-mode-definitions/generate-psk.xml.in b/op-mode-definitions/generate-psk.xml.in
new file mode 100644
index 000000000..69963f5be
--- /dev/null
+++ b/op-mode-definitions/generate-psk.xml.in
@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+<interfaceDefinition>
+  <node name="generate">
+    <children>
+      <node name="psk">
+        <properties>
+          <help>Generate PSK key</help>
+        </properties>
+        <children>
+          <node name="random">
+            <properties>
+              <help>Generate random hex PSK key</help>
+            </properties>
+            <command>${vyos_op_scripts_dir}/generate_psk.py</command>
+            <children>
+              <tagNode name="size">
+                <properties>
+                  <help>Key size in bytes</help>
+                </properties>
+                <command>${vyos_op_scripts_dir}/generate_psk.py --hex_size "$5"</command>
+              </tagNode>
+            </children>
+          </node>
+        </children>
+      </node>
+    </children>
+  </node>
+</interfaceDefinition>