Enhancement: quota and group manual CSVs should use persistent_path

[zoidy]

Summary
Currently, the manual override files for portal and quota are set in config/figshare.ini to be config/portal_manual.csv and config/quota_manual.csv respectively. These files should not be stored in config. Instead they should be stored in the directory identified by the persistent_storage setting in figshare.ini. Currently, in production, this has been done at the file system level by a symlink to the persistent_storage folder. However, this could cause some inconvenience if we need to re-deploy ReQUIAM as the link would need to be manually created. More generally, it would be good to have all customized files consistently live on persistent_storage which is defined by code rather than done at the file system level using links.

Objectives
quota_manual.csv and portal_manual.csv should be stored in the persistent_storage directory.

Proposal
Modify the code to use persistent_storage instead of the hard-coded config folder

Testing notes

• Test that the folder is writable
• Test that existing csv can be read from that folder

Additional notes

Implemented in: TBD