allow api credentials through dashboard instead of env

[aryanbhosale]

As @peterdudfield had mentioned in #170
run a general api and a general dashboard. This could even be a public api / dashboard
Then the users can

1. Enter a site details(their credentials that are now in env file)
   2a. Get a forecast with no live data
   2b. Get a forecast with live data, by entering credentials for that inverter.

[Clemo97]

Hey @aryanbhosale and @peterdudfield do we want the inverter values entered by the user to persist or be temporary such that the values reset on app refresh/restart?

[aryanbhosale]

Hey @aryanbhosale and @peterdudfield do we want the inverter values entered by the user to persist or be temporary such that the values reset on app refresh/restart?

Ideally the values should persist upon refreshing the page at least, upon restart perhaps some default values could be shown