Add Envoy sidecar for consistent hashing algorithm (#108)

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.
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**Documentation and Versioning Updates**
- Updated the version to 7.2.0 in `Chart.yaml` and `README.md` to
reflect the new release.
[[1]](diffhunk://#diff-58460ff3a5cd0697e7a245efcb688afe5bc5936a764a6d3b2fe92230310a013fL7-R7)
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- Expanded the changelog with an entry for 7.2.0 describing the Envoy
sidecar addition.
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- 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.
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**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.

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Co-authored-by: Ingvarr Zhmakin <[email protected]>

Document Engine: minor default DB tweak (#105)

Dashboard minor improvements (#104)

* Adds summary in Grafana dashboard
* Minor reorganizations

Document Engine: fix Grafana dashboard timeline (#102)

Document Engine: fix Redis TTL setting, S3 and Redis secrets definiti…

…on (#92)

Co-authored-by: Ingvarr Zhmakin <[email protected]>

Document Engine: Update Grafana dashboard (#100)

## Summary
Enhanced the Document Engine dashboard from 30 to 63 panels, adding
comprehensive observability across all system components.

  ## Changes
- **Added 8 new sections**: PostgreSQL, Redis Cache, Memory Cache,
HTTP/2 Streaming, Remote Documents, Document Conversion, Digital
Signatures, Queue Drops & Errors
- **Split Erlang VM memory**: Separate panels for Process, Binary, ETS,
and Atom memory
- **Added emojis**: All 14 sections now have emoji prefixes for better
navigation
- **Optimized queries**: Replaced `delta()` with `increase()` for
counters, removed redundant filters
- **Removed unused variable**: Cleaned up `erlang_memory_detail_metrics`
variable
  - **Better organization**: Logical grouping of related metrics

  ## New Metrics Covered
  - PostgreSQL: query duration, connection pool, decode time
  - Redis: cache hits/misses, operations, errors (when enabled)
  - Memory cache: hit/miss rates and ratios
  - HTTP/2: worker checkout time, render tile duration, process creation
  - Remote documents: TTFB and download time
  - Document conversion: conversion duration and rate
  - Digital signatures: signing, certificates, timestamps (when enabled)
  - Queue management: dropped requests and fallback hits

---------

Co-authored-by: Ingvarr Zhmakin <[email protected]>

Document Engine 1.12.2 (#99)

DE: document bulk deletion controls (#98)

Document Engine 1.12.1 (#97)

Document Engine 1.12.0 (#96)