Improve queries

[karimkawambwa]

Description

• Calculate data stats in chunks
• Retrieving stats with more granularity

Continue using the datastat table instead of querying the data values table until we are sure about performance (future proofing). #60

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

[kilemensi]

🚀 @karimkawambwa

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We need to update API docs then: https://github.com/CodeForAfrica/sensors.AFRICA/wiki/APIs#v2