Don’t auto-connect sensors on app startup

Problem statement:
Users open the Carv app not only when going skiing but also at home just to check their data etc. Regardless, the app always tries to connect to the sensors. This:

• wastes both the phone and sensor battery
• produces annoying LED flashes if your sensors are in your line of sight

Proposed solution:
Sensor connection shall be configurable by a three state config item:

• Auto-connect (always tries to connect on app startup)
• Prompt during startup (prompts the user if the sensors shall be connected on app startup)
• Never connect automatically (self-explanatory)

The "Prompt during startup" option shall be default. The displayed prompt might also contain a link to the configuration where this can be configured. When starting the skiing activity without connected sensors, the app shall show info about sensors being connected (again, there can be a link to the configuration so that users can customize the behavior to their liking).