[MAJOR BUMP] Remove unsupported config var substitution

[joshua-stauffer]

There is an undocumented code path which allows using the syntax $MY_SENSITIVE_VALUE for defining sensitive values in config to be replaced at runtime. This is not a supported path, and can lead to credentials being accidentally logged in the case that a sensitive field (password etc) contains the character $, which triggers the substitution logic. This PR removes that unsupported path and updates the documentation for clarity.

[netlify]

✅ Deploy Preview for niobium-lead-7998 canceled.

Name	Link
🔨 Latest commit	471c6c6
🔍 Latest deploy log	https://app.netlify.com/projects/niobium-lead-7998/deploys/69a1facf62e3b700082dbd73

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.57%. Comparing base (dad8cde) to head (471c6c6).
⚠️ Report is 15 commits behind head on develop.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #11690   +/-   ##
========================================
  Coverage    84.57%   84.57%           
========================================
  Files          472      472           
  Lines        39157    39157           
========================================
  Hits         33117    33117           
  Misses        6040     6040           

Flag	Coverage Δ
3.10	73.46% <100.00%> (ø)
3.10 athena	?
3.10 aws_deps	?
3.10 big	?
3.10 clickhouse	?
3.10 filesystem	?
3.10 mysql	?
3.10 openpyxl or pyarrow or project or sqlite or aws_creds	?
3.10 postgresql	?
3.10 spark	?
3.10 spark_connect	?
3.10 sql_server	?
3.10 trino	?
3.11	73.50% <100.00%> (ø)
3.11 athena	?
3.11 aws_deps	?
3.11 big	?
3.11 clickhouse	?
3.11 filesystem	?
3.11 mysql	?
3.11 openpyxl or pyarrow or project or sqlite or aws_creds	?
3.11 postgresql	?
3.11 spark	?
3.11 spark_connect	?
3.11 sql_server	?
3.11 trino	?
3.12	73.51% <100.00%> (ø)
3.12 athena	?
3.12 aws_deps	?
3.12 big	?
3.12 filesystem	?
3.12 mysql	?
3.12 openpyxl or pyarrow or project or sqlite or aws_creds	?
3.12 postgresql	?
3.12 spark	?
3.12 spark_connect	?
3.12 sql_server	?
3.12 trino	?
3.13	73.51% <100.00%> (ø)
3.13 athena	41.94% <50.00%> (ø)
3.13 aws_deps	45.20% <50.00%> (ø)
3.13 big	55.25% <100.00%> (ø)
3.13 bigquery	51.19% <50.00%> (ø)
3.13 clickhouse	41.96% <50.00%> (ø)
3.13 databricks	52.97% <50.00%> (ø)
3.13 filesystem	64.34% <100.00%> (ø)
3.13 gx-redshift	51.35% <50.00%> (ø)
3.13 mysql	51.75% <50.00%> (ø)
3.13 openpyxl or pyarrow or project or sqlite or aws_creds	59.90% <100.00%> (ø)
3.13 postgresql	55.11% <100.00%> (ø)
3.13 snowflake	53.84% <100.00%> (+<0.01%)	⬆️
3.13 spark	55.91% <100.00%> (ø)
3.13 spark_connect	46.86% <50.00%> (ø)
3.13 sql_server	53.17% <50.00%> (ø)
3.13 trino	48.70% <50.00%> (ø)
cloud	0.00% <0.00%> (ø)
docs-basic	59.19% <100.00%> (ø)
docs-creds-needed	57.82% <100.00%> (+0.03%)	⬆️
docs-spark	57.27% <50.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.