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_all_host_groups_query.graphql

@@ -0,0 +1,18 @@
+### Query
+# Use this query to list all host groups.
+
+```graphql
+query AllHostGroups($search_name: String) {
+  allHostGroups(search_name: $search_name) {
+    groupid
+    name
+  }
+}
+```
+
+### Variables
+```json
+{
+  "search_name": "Baustellen-Devices/*"
+}
+```