[Windows] Security model for files permissions - STEP 1 (#6893)

This PR is the first part of #6497 to ease the integration, following the new plan propose by @bmw here: #6497 (comment)

This step 1 refactor existing certbot.compat module into certbot.compat.misc, without any logic changed. Package certbot.compat will host the new modules that constitute the security model for Windows.

* Create the certbot.compat package. Move logic in certbot.compat.misc

* Add doc

* Fix lint

* Correct mypy

* Update client.py

certbot/account.py

@@ -7,22 +7,21 @@ import os
 import shutil
 import socket
 
-from cryptography.hazmat.primitives import serialization
 import josepy as jose
 import pyrfc3339
 import pytz
 import six
 import zope.component
+from cryptography.hazmat.primitives import serialization
 
 from acme import fields as acme_fields
 from acme import messages
 
-from certbot import compat
 from certbot import constants
 from certbot import errors
 from certbot import interfaces
 from certbot import util
-
+from certbot.compat import misc
 
 logger = logging.getLogger(__name__)
 
@@ -141,7 +140,7 @@ class AccountFileStorage(interfaces.AccountStorage):
     """
     def __init__(self, config):
         self.config = config
-        util.make_or_verify_dir(config.accounts_dir, 0o700, compat.os_geteuid(),
+        util.make_or_verify_dir(config.accounts_dir, 0o700, misc.os_geteuid(),
                                 self.config.strict_permissions)
 
     def _account_dir_path(self, account_id):
@@ -324,7 +323,7 @@ class AccountFileStorage(interfaces.AccountStorage):
 
     def _save(self, account, acme, regr_only):
         account_dir_path = self._account_dir_path(account.id)
-        util.make_or_verify_dir(account_dir_path, 0o700, compat.os_geteuid(),
+        util.make_or_verify_dir(account_dir_path, 0o700, misc.os_geteuid(),
                                 self.config.strict_permissions)
         try:
             with open(self._regr_path(account_dir_path), "w") as regr_file: