add support for Elasticsearch

[tomkralidis]

Description

Provide a repository plugin to connect to Elasticsearch

Additional Information

• HTTP based
• spatial support
• More info at overall docs

[tomkralidis]

Example implementation from @mikejmets https://github.com/SAEONData/pycsw/tree/elastic

[github-actions]

This Issue has been inactive for 90 days. In order to manage maintenance burden, it will be automatically closed in 7 days.

[tomkralidis]

Still valid/WIP

[github-actions]

This Issue has been inactive for 90 days. In order to manage maintenance burden, it will be automatically closed in 7 days.

[tomkralidis]

Unmarking as stale (adding as part of #1158)