created plugin to add users to a D1 nations group if they login from an IP address from one of those nations

[pascal-meunier]

Motivation: file permissions require a group for people from D1 nations. Filling the iplocation table of the network database with a copy of the ip ranges applicable to the D1 nations group is silly because that's a lot of rows to copy and it creates a management problem to keep the copy up to date. Instead, this plugin uses an SQL query with a join operation.

Does plg_user_purdue duplicate what plg_user_geo could do if it was configured to use the purdue group and the "pu" location? From what I can see both use custom locations in the iplocation table of the network database, in this case it would be the "pu" location
[7:09 PM]There's a need to put users from D1 nations into a group at login, so that the tool access limitation done in PHP can be mirrored in the filesystem permissions for /apps by setting UNIX acls using that group

Three files created under core/plugins/user/d1/:

• d1.php — on login, runs the JOIN query against the geo database. If no row is returned (IP not in any country group), returns immediately without touching group membership. If
  countrygroup == 'D1', adds the user to d1_nation. Any other countrygroup is logged but ignored. On account deletion, removes the user from d1_nation.
• d1.xml — extension manifest
• language/en-GB/en-GB.plg_user_d1.sys.ini — admin UI label (edited)

[pascal-meunier]

New commit: At login, if the user is a member of d1_approved, the plugin now removes them from d1_nation and returns without doing any geo database lookup. The existing geo-based logic runs only for users not in d1_approved.