feat: Add `UserMapping::has_system_and_nethsm_user`

Add a function to easily evaluate whether a `UserMapping` has a system
user and at least one NetHSM user.

Signed-off-by: David Runge <dvzrv@archlinux.org>

nethsm-config/src/mapping.rs

+#[cfg(doc)]
+use nethsm::NetHsm;
 use nethsm::{KeyId, SigningKeySetup, UserId};
 use serde::{Deserialize, Serialize};
 
@@ -616,4 +618,47 @@ impl UserMapping {
             } => vec![],
         }
     }
+
+    /// Returns whether the mapping has both system and [`NetHsm`] users.
+    ///
+    /// Returns `true` if the `self` has at least one system and one [`NetHsm`] user, and `false`
+    /// otherwise.
+    pub fn has_system_and_nethsm_user(&self) -> bool {
+        match self {
+            UserMapping::SystemNetHsmOperatorSigning {
+                nethsm_user: _,
+                nethsm_key_setup: _,
+                system_user: _,
+                ssh_authorized_key: _,
+                tag: _,
+            }
+            | UserMapping::HermeticSystemNetHsmMetrics {
+                nethsm_users: _,
+                system_user: _,
+            }
+            | UserMapping::SystemNetHsmMetrics {
+                nethsm_users: _,
+                system_user: _,
+                ssh_authorized_key: _,
+            }
+            | UserMapping::SystemNetHsmBackup {
+                nethsm_user: _,
+                system_user: _,
+                ssh_authorized_key: _,
+            } => true,
+            UserMapping::SystemOnlyShareDownload {
+                system_user: _,
+                ssh_authorized_keys: _,
+            }
+            | UserMapping::SystemOnlyShareUpload {
+                system_user: _,
+                ssh_authorized_keys: _,
+            }
+            | UserMapping::SystemOnlyWireGuardDownload {
+                system_user: _,
+                ssh_authorized_keys: _,
+            }
+            | UserMapping::NetHsmOnlyAdmin(_) => false,
+        }
+    }
 }