Release v5.2.0

Release notes:

• Add string field filtering;
• Add mixin fro handling the array fields operations;
• Add cache_key support for data endpoints and script endpoints;
• Add special error if user is not found;
• Saving a user saves now user_profile;
• Add query paramter to DataEndpoints
• Add proper user and group endpoints handling;
• Add Backup and PartialBackup models; with full CRUD;
• Fixes in library requests;
• Add possibility to restore backups;
• Add possibility to define instance global config;
• Add possibility to use template on DataEndpoint - on get();