feat: fix FileAdapter CSV format to preserve spaces after commas

[Copilot]

fix: #406

Tests were failing because FileAdapter::save_policy wrote CSV files without spaces after commas (p, alice,data1,read), while the original files had spaces (p, alice, data1, read). Tests with auto-save enabled modified shared example files, causing subsequent tests to fail on policy loading.

Changes:

• Updated FileAdapter::save_policy to use rule.join(", ") instead of rule.join(",") for both policy and grouping sections
• Strip trailing newline from generated CSV to match source file format

// Before
writeln!(policies, "{}, {}", ptype, rule.join(","))

// After  
writeln!(policies, "{}, {}", ptype, rule.join(", "))
// ...
if policies.ends_with('\n') {
    policies.pop();
}

This ensures policy files remain byte-identical after save operations, preventing test interference.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[bug] fix CI error</issue_title>
<issue_description>see: https://github.com/casbin/casbin-rs/actions/runs/20377041315/job/58558208590#step:13:220

[Auto Build CI (ubuntu-latest, beta)](https://github.com/casbin/casbin-rs/actions/runs/20377041315/job/58558208590#logs)
failed 18 minutes ago in 1m 49s

Cargo Test For All Features Using tokio

Run actions-rs/cargo@v1
/home/runner/.cargo/bin/cargo test --no-default-features --features runtime-tokio,cached,glob,ip,watcher,logging,incremental,explain
   Compiling casbin ***.17.0 (/home/runner/work/casbin-rs/casbin-rs)
    Finished `test` profile [unoptimized + debuginfo] target(s) in 6.09s
     Running unittests src/lib.rs (target/debug/deps/casbin-af3cc61c528878e1)

running 101 tests
test adapter::string_adapter::tests::test_save_policy ... ok
test adapter::string_adapter::tests::test_clear_policy ... ok
test adapter::string_adapter::tests::test_is_filtered ... ok
test cache::default_cache::tests::test_has_and_clear ... ok
test cache::default_cache::tests::test_set_and_get ... ok
test cached_enforcer::tests::test_send_sync ... ok
test config::tests::test_from_text ... ok
test config::tests::test_get ... ok
test enforcer::tests::test_custom_function_with_dynamic_types ... ok
test adapter::string_adapter::tests::test_load_policy ... ok
test enforcer::tests::test_enable_auto_save ... ok
test enforcer::tests::test_enforcer_swap_adapter_type ... ok
test enforcer::tests::test_filtered_file_adapter ... ok
test enforcer::tests::test_enforce_ex ... FAILED
test enforcer::tests::test_ip_match_model ... ok
test enforcer::tests::test_get_and_set_model ... ok
test enforcer::tests::test_key_match_model_in_memory_deny ... ok
test enforcer::tests::test_get_and_set_adapter_in_mem ... ok
test enforcer::tests::test_not_used_rbac_model_in_memory ... ok
test enforcer::tests::test_policy_abac1 ... ok
test enforcer::tests::test_keymatch_custom_model ... ok
test enforcer::tests::test_key_match_model_in_memory ... ok
test enforcer::tests::test_policy_abac2 ... ok
test enforcer::tests::test_send_sync ... ok
test enforcer::tests::test_rbac_model_in_memory ... ok
test enforcer::tests::test_rbac_model_in_memory_indeterminate ... ok
test error::tests::test_send_sync ... ok
test enforcer::tests::test_role_links ... ok
test management_api::tests::test_get_list ... FAILED
test enforcer::tests::test_set_role_manager ... ok
test frontend::tests::test_casbin_js_get_permission_for_user ... ok
test management_api::tests::test_get_policy_api ... FAILED
test management_api::tests::test_modify_grouping_policy_api ... FAILED
test management_api::tests::test_modify_grouping_policies_api ... FAILED
test management_api::tests::test_modify_policies_api ... FAILED
test model::default_model::tests::test_abac ... ok
test model::default_model::tests::test_basic_model ... ok
test management_api::tests::test_modify_policy_api ... FAILED
test model::default_model::tests::test_basic_model_no_policy ... ok
test model::default_model::tests::test_basic_model_with_root ... ok
test model::default_model::tests::test_basic_model_without_resources ... ok
test model::default_model::tests::test_basic_model_with_root_no_policy ... ok
test model::default_model::tests::test_basic_model_without_users ... ok
test model::default_model::tests::test_rbac_model_using_in_op ... FAILED
test model::default_model::tests::test_rbac_model_with_custom_data ... FAILED
test model::default_model::tests::test_rbac_model ... FAILED
test model::default_model::tests::test_rbac_model_with_deny ... ok
test model::default_model::tests::test_rbac_model_with_domains_at_runtime_mock_adapter ... ok
test model::default_model::tests::test_rbac_model_with_not_deny ... ok
test model::default_model::tests::test_rbac_model_with_domains ... ok
test model::function_map::tests::test_glob_match ... ok
test model::default_model::tests::test_rbac_model_with_domains_runtime ... ok
test model::function_map::tests::test_ip_match_panic_1 - should panic ... ok
test model::function_map::tests::test_key_get ... ok
test model::function_map::tests::test_ip_match ... ok
test model::function_map::tests::test_ip_match_panic_2 - should panic ... ok
test model::default_model::tests::test_rbac_model_with_resource_roles ... ok
test model::function_map::tests::test_key_match ... ok
test model::function_map::tests::test_key_match2 ... ok
test model::function_map::tests::test_key_match3 ... ok
test model::function_map::tests::test_key_match5 ... ok
test model::function_map::tests::test_regex_match ... ok
test rbac::default_role_manager::matching_bfs::test::test_max_depth ... ok
test rbac::default_role_manager::tests::test_basic_role_matching ... ok
test rbac::default_role_manager::tests::test_basic_role_matching2 ... ok
test rbac::default_role_manager::tests::test_clear ... ok
test rbac::default_role_manager::tests::test_cross_domain_role_inheritance_complex ... ok
test rbac::default_role_manager...

</details>



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- Fixes casbin/casbin-rs#406

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Benchmark for 7272c2a

Click to view benchmark

Test	PR Benchmark	Master Benchmark	%
b_benchmark_rbac_model_large	9.7±0.03ms	10.1±0.08ms	-3.96%
benchmark priority model	1471.8±15.80ns	1468.5±11.24ns	+0.22%
benchmark_abac_model	1074.9±16.53ns	1098.5±13.15ns	-2.15%
benchmark_basic_model	1217.7±37.03ns	1153.4±10.53ns	+5.57%
benchmark_key_match	4.0±0.05µs	4.1±0.04µs	-2.44%
benchmark_raw	0.0±0.00ns	0.0±0.00ns	NaN%
benchmark_rbac_model	3.3±0.04µs	3.3±0.04µs	0.00%
benchmark_rbac_model_medium	819.9±35.21µs	785.5±5.37µs	+4.38%
benchmark_rbac_model_with_domains	1996.2±32.09ns	2.1±0.02µs	-4.94%
benchmark_rbac_with_deny	5.3±0.06µs	5.3±0.07µs	0.00%
benchmark_rbac_with_resource_roles	1485.8±23.15ns	1430.3±9.18ns	+3.88%
benchmark_role_manager_large	4.2±0.02ms	4.2±0.01ms	0.00%
benchmark_role_manager_medium	268.3±4.32µs	268.5±4.14µs	-0.07%
benchmark_role_manager_small	84.0±1.51µs	81.3±0.62µs	+3.32%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (7272c2a) to head (8126594).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@      Coverage Diff      @@
##   master   #407   +/-   ##
=============================
=============================

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