Look up the air-quality source's own API key, not the weather source's

locationRequiresApiKey and the key lookup both used location.source (the
weather source) instead of location.airQualitySource. Every air-quality
source today happens to share a source with its weather counterpart, so
this never surfaced, but it breaks - and currently crashes via !! in
OpenWeatherRepository - whenever they differ and the air-quality source
needs a key the weather source doesn't.

app/src/main/java/com/pranshulgg/weather_master_app/data/repository/airquality/CacheResolverForAirQuality.kt

@@ -38,10 +38,10 @@ class CacheResolverForAirQuality @Inject constructor(
         val cache = dao.getAirQualityForLocation(location.id)
         val shouldReturnCache = shouldReturnAirQualityCache(cache, isManualRefresh, isForceRefresh)
 
-        val locationRequiresApiKey = location.source.requiresUserApiKey
+        val locationRequiresApiKey = location.airQualitySource.requiresUserApiKey
 
         val apiKey = if (locationRequiresApiKey)
-            apiKeysDao.getApiKeyForSource(location.source) else null
+            apiKeysDao.getApiKeyForSource(location.airQualitySource) else null
 
         val domain = cache.toDomain()