feat: Sample Feast job with ES publisher

[szczeles]

Summary of Changes

Feast sample job modified to not only do a Feast -> Neo4j extraction, but also Neo4j -> ES publishing. It's better suited for the demo purposes now.

Tests

No tests, only sample job modification. Sample job tested manually:

root@feast-loader:/# python sample_feast_loader.py feast-feast-core:6565 bolt://neo4j http://amundsen-elasticsearch-client:9200

WARNING:elasticsearch:GET http://amundsen-elasticsearch-client:9200/table_search_index/_alias [status:404 request:0.031s]
WARNING:databuilder.publisher.elasticsearch_publisher:Received index not found error from Elasticsearch. The index doesn't exist for a newly created ES. It's OK on first run.
root@feast-loader:/# 

Documentation

Header in the sample script with usage.

CheckList

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[szczeles]

@feng-tao Could you please have a look in spare time?