Create and edit stock portfolio flow

[horvathmarton]

Description

We need a way for the user to create new stock portfolios and edit the name and descriptions of existing ones.

Technical details

• The API endpoints already exist here (POST/PATCH - /stocks/portfolios).
• The payload format is { name: string; description: string }.
• [x] This functionality should be placed on the portfolio view.
• [x] Probably a modal is the easiest way to introduce the creation flow.
• [x] Loading state should be handled properly.
• [x] Possible errors:
  • [x] 400 - malformed payload
  • [x] ~401 - the user is not autheticated~ (this is a possible error, but should not happen in this state of the frontend)
  • [x] 403 - the user is not allowed to create portfolios
  • [x] 500 - unhandled error