[pgAdmin4][Patch]: RM #3674 Old session files are not cleared in .pgAdmin session and keep piling up

Hi Hackers

Attached is the patch to fix the RM #3674 "Old session files are not
cleared in .pgAdmin session and keep piling up". Patch contains following
changes:

- With current implementation we have override *get_expiration_time*()
method of flask and return the expiry time as "datetime.datetime.now() +
1 day (hard coded)". Also the time used as *now*() instead of *utcnow*()
which is there in base class method of flask.
- *Solution*: We should use *session.permanent *flag and set
the *permanent_session_lifetime
*variable of app. I have remove the overridden function and set the
session.permanent flag to True, and set the
permanent_session_lifetime with
the specified value in config.py. Added new configuration parameter
"SESSION_EXPIRATION_TIME_IN_DAYS".
- Added CHECK_SESSION_FILES_INTERVAL configuration parameter in Hour
with default value is 24. This is an interval to check the session files
for the cleanup.

--
*Akshay Joshi*

*Sr. Software Architect *

*Phone: +91 20-3058-9517Mobile: +91 976-788-8246*