Resolve #3353017 "Provide a secret"

Closes #3353017

config/schema/parameters.schema.yml

@@ -207,3 +207,14 @@ parameter.icon:
     value:
       type: string
       label: 'Raw stored icon'
+
+parameter.secret:
+  type: parameter_plugin
+  label: 'Secret'
+  mapping:
+    value:
+      type: string
+      label: 'Encrypted value'
+    encoding:
+      type: ignore
+      label: 'Settings needed for decryption'