app_settings.model library Null safety

1. irte_engine
2. app_settings.model library

irte_engine package

1. Libraries
2. adapter_factory
3. adapters
4. alias
5. api_endpoint.interface
6. app_settings
7. app_settings.bindings
8. app_settings.model
9. app_settings_controller
10. app_state
11. app_state.bindings
12. app_state.enum
13. app_state_controller
14. apple.adapter
15. apple_auth_credentials.model
16. auth
17. auth.bindings
18. auth_adapter.enum
19. auth_adapter.interface
20. auth_authenticated_load_user.listener
21. auth_client
22. auth_controller
23. auth_credentials.model
24. auth_payload.model
25. auth_social_payload.model
26. auth_status.enum
27. auth_token.model
28. auth_unauthenticated_remove_user.listener
29. auth_workflow_controller
30. client
31. credentials.adapter
32. database
33. database_item
34. database_storage
35. engine.bindings
36. engine.config
37. engine.modules
38. engine.version
39. enums
40. event_listener.interface
41. extensions
42. facebook.adapter
43. full_name
44. identifiable.interface
45. in_range
46. interfaces
47. interfaces
48. irte_database
49. irte_engine
50. json
51. key_value_storage
52. list_map_key
53. memory_storage
54. minor_plugin_event
55. models
56. models
57. models
58. models
59. models
60. name.interface
61. payload
62. plugin_event
63. plugin_priority.enum
64. rest
65. simple_storage
66. storage
67. storage.bindings
68. successful_response
69. to_json
70. user
71. user.bindings
72. user.model
73. user_controller
74. user_management
75. workflow
76. workflow
77. workflow
78. workflow_container
79. workflow_controller.interface
80. workflow_listener.interface