Implement saving a record

[nivisi]

After #7 is done, we are now able to finish adding a record. On the page, at the moment, the only data that we can enter is title, description and url

We need to:

• Configure the corresponding method in the repository
• Create a use case for creating a record
• Implement the logic on the cubit side
• Add the save button to the app bar
• Pass the data from the page to the cubit

We'll work on validation in #9