Fetches and caches pollendata from https://pollenvarsel.naaf.no/charts/forecast.

• /regions - lists available regions
• /pollen/{region} - pollen data for {region}
• /forecast/{region} - text forecast for {region}
• /combined/{region} - combined pollen data and text forecast for {region}

The levels describe the amount of pollen grains per m3 of air.

• 0 - No spread (0)
• 1 - Low spread (1 - 9)
• 2 - Moderate spread (10 - 99)
• 3 - Heavy spread (100 - 999)
• 4 - Extreme spread (1000+)