Finetuning Program

[andronisdre]

All our branches need to be merged to main before starting this issue

• [x] Test the full program with all endpoints extensively in postman
• [x] Make small adjustments and fix eventual bugs
• [x] check that everything looks nicely structured in the code and eventually add comments if needed
• [x] see that when a document is deleted that it only says "document deleted" in the case that the document exists and is deleted.
• [ ] see that ids are being checked correctly when doing get all DTO in all collections
• [x] add so that an auctions end date has to be later than created_At date
• [x] change startingBid field to startingPrice
• [x] remove id field from auctionDTO
• [x] test the whole chain from creating a user to creating an auction with that user and creating orders etc