fix: redis sentinel secret missing

[james-d-elliott]

Adds the redis sentinel secret and refactors the entire secret derivation process to make it more consistent.

[authelia]

Artifacts

These changes are published for testing on Buildkite and DockerHub.

Docker Container

• docker pull authelia/authelia:fix-redis-sentinel-password-secret

[codecov]

Codecov Report

Merging #1839 (693657f) into master (7ccbaaf) will increase coverage by 0.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1839      +/-   ##
==========================================
+ Coverage   71.80%   71.99%   +0.18%     
==========================================
  Files         152      152              
  Lines        4313     4313              
  Branches      177      177              
==========================================
+ Hits         3097     3105       +8     
+ Misses        991      985       -6     
+ Partials      225      223       -2     

Flag	Coverage Δ
backend	73.75% <100.00%> (+0.11%)	⬆️
frontend	65.20% <ø> (+0.44%)	⬆️

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

Impacted Files	Coverage Δ
internal/configuration/validator/authentication.go	100.00% <ø> (+2.98%)	⬆️
internal/configuration/validator/configuration.go	100.00% <ø> (ø)
internal/configuration/reader.go	95.00% <100.00%> (-0.75%)	⬇️
internal/configuration/validator/keys.go	100.00% <100.00%> (ø)
internal/configuration/validator/secrets.go	84.37% <100.00%> (+4.37%)	⬆️
internal/configuration/validator/storage.go	100.00% <100.00%> (ø)
web/src/hooks/IntermittentClass.ts	76.47% <0.00%> (+23.52%)	⬆️