Sensor source ids are not created equally across the different fetchers

[caparker]

The source id is used to match measurement data to the sensor in the openaq db and they are not being done the same which could cause issues if there is ever the case where two different sources have the same source site id value.

For example, the purpleair fetcher provides this format
PurpleAir-35053-10.0_um_count, which is
SourceName-SourceSiteId-SourceParameterAndUnitsName
Whereas clarity provides
AX5CC5K1-pm10, which is
SourceSiteName-OpenAQParameterName

I propose that we do the following

• Exchange the dashes for forward slashes
• Always include the SourceName
• Always use SourceSiteId instead of SourceSiteName
• Aways use the OpenAQParameterAndUnitsName
• Include the SourceSystemId or a suitable identifier that could be derived from the source

Which would look like this
SourceName/SourceSystemId/SourceSiteId/OpenAQParameterAndUnits
E.g.
PurpleAir/PAII/35053/pm10count