Implement cashflow management feature

[PedroHFreire]

We need to handle portfolio cash properly. This involves several sub-tasks:

• Inserting the update_portfolio_assets function into the stock_history script as discussed in the 'stabledb bugs' chat.

• Creating a cash balance system using a trigger to automatically insert the cash transactions related to the buying and selling of assets.

• Updating the portfolio_assets table with the update_portfolio_assets function for 'Cash' as an asset in the assets table.

[PedroHFreire]

• Cashflow Management:
  • Use the last two messages at the chatgpt "stabledb bugs" chat to insert the update_portfolio_assets function into the stock_history script.
  • Implement a cashflow management feature into the database to handle portfolio cash properly.
  • Create a cash balance system (potentially using a trigger to automatically insert the cash transactions related to the buy and sell of assets) and update the existing database according to initial inserts.
  • As "Cash" is an asset in the assets table, it should also be updated in the portfolio_assets table with the update_portfolio_assets function.

[PedroHFreire]

• The update_portfolio_assets function was created inside the update_functions script and it updates the quantities fo a given asset for a given portfolio since a specified dat.
• For this was created a insert_transaction function that is responsible for inserting transactions into the database, for every asset that is transactioned there is a corresponding inverse cash transaction inserted.
• It was created an insert transaction GUI to insert the transactions correctly and updating the quantities of the asset transactioned and the cash balance, but this is still ongoing development