Improve on veeeery long cold start times

[rene78]

The cold start time of the functions is around 10s. Definitely not acceptable. Current workaround is to first use copy of portfolio in local storage to display portfolio table and update prices later, if database entry is newer. But this does not take the creation of a new portfolio into account. Thus users have to wait for around 10s, until there new portfolio is saved to the database. Possible ways to mitigate:

• Implement a "warm-up" function call, when user opens "Create/Edit Portfolio". See this example.
• Use C# instead of node.js
• Avoid using npm package "Mongoose", if at all possible