This PR resolves #1439 by adding integration tests for the REST Catalog.

Functionality testing against the server can be simulated to a certain degree, but some checks are very hard to emulate for example, triggering a 500 response from the server or getting information from the request which is abstracted away by the catalog.

Here is the lists of the tests that were successfully created in this integration testing:

1. test_create_namespace_200
2. test_create_namespace_if_exists_409
3. test_list_namespaces_200
4. test_create_namespace_409
5. test_drop_namespace_404
6. test_drop_namespace_409
7. test_load_namespace_properties_200
8. test_load_namespace_properties_404
9. test_update_namespace_properties_200
10. test_update_namespace_properties_404
11. test_namespace_exists_204
12. test_namespace_exists_404
13. test_namespace_empty
14. test_load_table_200
15. test_load_table_honor_access_delegation
16. test_load_table_from_self_identifier_200
17. test_list_tables_200
18. test_list_tables_200_sigv4
19. test_list_tables_404
20. test_load_table_404
21. test_table_exists_204
22. test_table_exists_404
23. test_drop_table_404
24. test_create_table_200
25. test_create_table_with_given_location_removes_trailing_slash_200
26. test_create_staged_table_200
27. test_create_table_409
28. test_create_table_if_not_exists_200
29. test_delete_namespace_204
30. test_delete_table_204
31. test_delete_table_from_self_identifier_204
32. test_delete_table_404
33. test_rename_table_200
34. test_rename_table_from_self_identifier_200
35. test_create_table_missing_namespace
36. test_load_table_invalid_namespace
37. test_drop_table_invalid_namespace
38. test_purge_table_invalid_namespace
39. test_create_namespace_invalid_namespace
40. test_drop_namespace_invalid_namespace
41. test_load_namespace_properties_invalid_namespace
42. test_update_namespace_properties_invalid_namespace
43. test_request_session_with_ssl_client_cert
44. test_create_namespace_if_not_exists
45. test_create_namespace_if_already_existing
46. test_list_views_200_sigv4
47. test_list_views_404
48. test_drop_view_invalid_namespace
49. test_drop_view_404
50. test_properties_sets_headers
51. test_no_uri_supplied

There are some tests that are either skipped or were not applicable to the integration test or producing incorrect results.

Here is the full list:

1. test_catalog_from_environment_variables
2. test_catalog_from_environment_variables_override
3. test_catalog_from_parameters_empty_env
4. test_config_200
5. test_config_sets_headers
6. test_create_table_419
7. test_drop_view_204
8. test_list_namespace_with_parent_200
9. test_list_namespaces_token_expired
10. test_list_views_200
11. test_namespace_exists_200
12. test_namespace_exists_500
13. test_register_table_200
14. test_register_table_409
15. test_request_session_with_ssl_ca_bundle
16. test_table_exists_200
17. test_table_exists_500
18. test_table_identifier_in_commit_table_request
19. test_token_200
20. test_token_200_w_auth_url
21. test_token_200_without_optional_fields
22. test_token_400
23. test_token_401
24. test_token_with_custom_scope
25. test_token_with_default_scope
26. test_token_with_optional_oauth_params
27. test_token_with_optional_oauth_params_as_empty