Adding some aggregation endpoints

[machakux]

I was assuming a resources collection might accommodate multiple resource types, then resources can be classified by type through facility_code.

Examples:

/api/<facility_code>/values/region
/api/<facility_code>/count/region
/api/<facility_code>/sum/region/population_served

I would prefer to use endpoint instead of facility_code (i.e something like /api/waterpoints/values/region instead of /api/wp001/values/region) for the sake of consistency & prettier URLs but I haven't figured how to do that without an extra database query unless facility_code values are equal endpoints. Is there a more convenient way to resolve this or should I just assume there will be one resource type per instance?

[kynan]

I agree it would be nicer to use the endpoint rather than the facility_code. I don't have a good idea how to implement it though. You could potentially fire the get request through eve, however that requires to set up the right flask request context which I don't remember how to do. What you have is a reasonable start I think.

[dgorissen]

Note wp001 is just something I made up. AFAIK this is completely arbitrary and there is no guidance or standard around what facility_code should be. In an ideal world this would be set by the administrative entity.

No reason we can't rename wp001 to something more friendly. Without any further information trying to come up with a scheme mapping onto is not worth it IMO.

[machakux]

I have added endpoints for retrieving group difference, ratio and sum of product of two fields.