Review/refactoring meta issue

[jonasraoni]

• Review user issues in the forum
• Review the "Refresh" button: perhaps it can happen automatically
• Replace serialize/unserialize by JSON
• Remove deprecated code (Config::getVar('i18n', 'client_charset'), AppLocale, etc)
• Attempt to use the newer jobs module and get rid of Acron/TaskScheduler checks
• Add auto-formatting for the code
• include_once('Archive/Tar.php') not needed (Remove the PEAR/Archive_Tar requirement #25)
• Use namespaces
• Use PHP 8 features
• Replace the binary flags by fields: it's complex to view/deal with, better to get it replaced by something simpler (e.g. state machine)
• Remove non-visited code branches
• Attempt to use events to detect modifications on the issues/submissions (useful only if the code which looks for modifications is heavy)
• Review states by checking the ones available in pkppln and locks-o-matic: (Missing mapping for the processing state: harvest-error #20 + Missing mapping for the "inProgress" state #18)
• Remove non-used locale keys
• Update README with better instructions (how-to images, troubleshooting, etc) and link/reuse the content inside the plugin
• Rename PLN to PN (renaming the folder might be problematic)
• The forum is often orientating users to reset deposits. Sometimes it doesn't make sense, thus this feature should be better controlled.