[Auth] Allow for configuring a custom server

[vishnukvmd]

Description

Users can now tap on the onboarding screen 7 times to bring up a page where they can configure the endpoint the app should be connecting to.

Tests

• Verified that production flows are working as expected
• Verified that configuring the endpoint to a local instance lets you
  • Connect to that instance
  • Create an account
  • Add a key
  • Modify a key
  • Logout and log back in

[ua741]

Should we show the server url on UI when it's not the production endpoint (https://api.ente.io)

As this url will be cleared on logout, it will be probably helpful when it's shown during login/sign up and may be the in hamburger menu below version.

[vishnukvmd]

Should we show the server url on UI when it's not the production endpoint (https://api.ente.io)

As this url will be cleared on logout, it will be probably helpful when it's shown during login/sign up and may be the in hamburger menu below version.

Done. Have also added a check to /ping to verify the endpoint.