Stand Architecture - refactored by new requirements

[realtek2]

folder with new and updated endpoints in postman: https://winter-robot-21254.postman.co/workspace/Meeting-KB~8c31ab98-8bce-439c-bf8e-d6146a360a6d/folder/10527081-0623903a-cc47-425e-8d9f-c31403de6b3b?ctx=documentation

• added new endpoints for creating/editing/removing stand template
• changed stand_template table structure
• removed stand_publishers
• added stand_records and pivot table
• changed users columns names
• refactored GET stand/templates endpoint for FE's convenience template using
• added new endpoints to register/update/unsubscribe from stand template for publishers and responsible
• removed leftovers and others code style fixed