Remove third party dot env and replace with own env class

[necessarylion]

No description provided.

[github-actions]

Coverage after merging rewrite-dot-env into develop

73.91%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
lib
app.dart	100%	100%	93.10%	46, 47
lib/auth
auth.dart	100%	100%	0%	13, 25, 4, 6
lib/config
app_config.dart	100%	100%	40%	52, 54, 56
lib/db
db_driver.dart	100%	100%	50%	3
lib/env
env.dart	100%	100%	100%
lib/exception
http_exception.dart	100%	100%	100%
internal_error_exception.dart	100%	100%	100%
not_found_exception.dart	100%	100%	100%
query_exception.dart	100%	100%	100%
unauthorized_exception.dart	100%	100%	100%
validation_exception.dart	100%	100%	100%
lib/ioc
ioc_container.dart	100%	100%	100%
lib/request
form_request.dart	100%	100%	13.95%	..., 92, 93, 97, 98
dox_request.dart	100%	100%	58.14%	..., 27, 46, 47, 48
request_file.dart	100%	100%	0%	..., 48, 49, 50, 7
form_data_visitor.dart	100%	100%	0%	..., 75, 78, 79, 82
lib/response
dox_cookie.dart	100%	100%	100%
dox_response.dart	100%	100%	100%
serializer.dart	100%	100%	86.67%	18, 19
lib/router
router.dart	100%	100%	50%	2
route.dart	100%	100%	86.90%	..., 91, 92, 95, 97
route_data.dart	100%	100%	100%
http_response_handler.dart	100%	100%	88.89%	43, 44
http_request_handler.dart	100%	100%	81.71%	..., 41, 42, 54, 55
lib/server
dox_server.dart	100%	100%	81.82%	..., 61, 64, 65, 71
lib/utils
extensions.dart	100%	100%	100%
global.dart	100%	100%	100%
hash.dart	100%	100%	100%
aes_encryptor.dart	100%	100%	100%
logger.dart	100%	100%	40%	..., 27, 28, 3, 4
utils.dart	100%	100%	100%
lib/validation
dox_validator.dart	100%	100%	93.02%	102, 33, 38
nested_validation_visitor.dart	100%	100%	100%
rules.dart	100%	100%	78.57%	..., 286, 95, 97, 98
validation_item.dart	100%	100%	100%
lib/websocket
socket_emitter.dart	100%	100%	6.25%	..., 55, 56, 58, 59
dox_websocket.dart	100%	100%	88%	59, 65, 66
socket_storage.dart	100%	100%	89.29%	60, 69, 70
web_socket_info.dart	100%	100%	100%