Changes API for external backends

[sirex]

Implement Changes API for external data backends.

For this to work, we need a background task, which would scan for changes and write patches to separate database.

This could be done wit a new command:

spinta changes scan

This command would scan changes in the most efficient way and write changed data to changes table.

When a /:changes request would be made to external backend, then data from prepopulated changes table would be read.

To make this work, we might use Kafka, to monitor changes and write changed data to changes table.

Also it would be an option, to take changes directly from Kafka.

If Kafka is too heavy, we should consider another Change Data Capture (CDC) solution.

Depends on

• LDES palaikymas (Changes API / Data streaming) ivpk/uapi#22

Related

• Pull only changed data #42
• Cooperating backends (_id) #661