Revert "Remove "caching" for repository"

This reverts commit a10f7b768a5876885a8c128381b7ce38dd990cf7.
Static Find method for the Category model
Split Repository into CsvRepository and SqlRepository
Send event when new order has been added
Cleanup 'using' in files
Show the repository works
Follow new subsystem diagram
Batch update/deletion for events possible
Edit SE part for assignment 39
Add SE content for assignment 40
sdd update
Use the adapter pattern design for Google
Move only interface to new Interfaces folder
Use the bridge pattern for data storage
Add failure cases to SDD
Add reporting module with DTO classes
Add reporting module to project
Implement the factory pattern for data storage
Addition to factory pattern
Implement strategy pattern