Add Envoy sidecar for consistent hashing algorithm

[bszaf]

This pull request introduces version 7.2.0 of the Document Engine Helm chart. The main change is the addition of Envoy as an optional sidecar container, enabling consistent hashing for improved load distribution. The documentation and configuration files have been updated to reflect this new feature, and a minimal test configuration for the Envoy sidecar has been added.

New Feature: Envoy Sidecar for Consistent Hashing

• Added support for deploying Envoy as an optional sidecar to enable consistent hashing by document ID, which helps with better load distribution. This includes new configuration options in values.yaml and documentation updates. [1] [2] [3]

Documentation and Versioning Updates

• Updated the version to 7.2.0 in Chart.yaml and README.md to reflect the new release. [1] [2]
• Expanded the changelog with an entry for 7.2.0 describing the Envoy sidecar addition. [1] [2]
• Adjusted documentation tables and anchor links in README.md to include new Envoy sidecar options and account for shifted line numbers due to the new configuration. [1] [2] [3] [4] [5] [6] [7] [8] [9]

Testing and CI

• Added a minimal test configuration file (ci/05-envoy-sidecar-values.yaml) to validate the Envoy sidecar and consistent hashing setup, including multiple replicas and headless service for pod discovery.
• Updated CI documentation to describe the new Envoy sidecar test scenario.

[lazyoldbear]

NetworkPolicy — needs to be updated.

[lazyoldbear]

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