feat: add comprehensive tests and samples for host and user rights endpoints

- Added GraphQL sample queries and mutations for host and user rights endpoints in the 'docs' directory.

- Implemented unit tests for all remaining GraphQL endpoints, including hosts, devices, host groups, locations, and user permissions.

- Created dedicated integration tests for host and user rights workflows, utilizing the new sample files.

- Fixed a bug in 'HostImporter.getHostGroupHierarchyNames' to correctly process and sort nested host group hierarchies.

- Refined Zabbix API mocking in tests to improve reliability and support path-based routing.

- Verified all 38 tests across 11 suites pass successfully.

docs/sample_export_user_rights_query.graphql

@@ -0,0 +1,28 @@
+### Query
+Use this query to export all user rights (roles and groups).
+
+```graphql
+query ExportUserRights($name_pattern: String) {
+  exportUserRights(name_pattern: $name_pattern) {
+    userGroups {
+      usrgrpid
+      name
+      hostgroup_rights {
+        name
+        permission
+      }
+    }
+    userRoles {
+      roleid
+      name
+    }
+  }
+}
+```
+
+### Variables
+```json
+{
+  "name_pattern": "Admin%"
+}
+```