feat(configuration): mtls clients

[james-d-elliott]

This implements mTLS support for LDAP, Redis, and SMTP. Specified via the tls.certificate_chain and tls.private_key options.

Closes #4044

[authelia]

Artifacts

These changes are published for testing on Buildkite, DockerHub and GitHub Container Registry.

Docker Container

• docker pull authelia/authelia:feat-mtls-clients
• docker pull ghcr.io/authelia/authelia:feat-mtls-clients

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[codecov]

Codecov Report

Merging #4221 (72baca6) into master (6e835bd) will increase coverage by 0.46%.
The diff coverage is 60.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4221      +/-   ##
==========================================
+ Coverage   66.75%   67.21%   +0.46%     
==========================================
  Files         262      263       +1     
  Lines       17985    18122     +137     
  Branches      431      431              
==========================================
+ Hits        12006    12181     +175     
+ Misses       5243     5210      -33     
+ Partials      736      731       -5     

Flag	Coverage Δ
backend	67.64% <60.42%> (-0.15%)	⬇️
frontend	62.45% <ø> (+4.96%)	⬆️

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

Impacted Files	Coverage Δ
internal/configuration/schema/types.go	59.03% <15.68%> (-12.73%)	⬇️
internal/utils/crypto.go	71.31% <42.85%> (-2.47%)	⬇️
internal/configuration/decode_hooks.go	92.48% <68.51%> (-3.76%)	⬇️
internal/configuration/validator/shared.go	73.91% <73.91%> (ø)
internal/authentication/ldap_user_provider.go	91.71% <100.00%> (ø)
internal/configuration/provider.go	86.30% <100.00%> (+0.38%)	⬆️
internal/configuration/validator/authentication.go	100.00% <100.00%> (+2.89%)	⬆️
internal/configuration/validator/notifier.go	81.94% <100.00%> (+6.18%)	⬆️
internal/configuration/validator/session.go	100.00% <100.00%> (ø)
internal/notification/smtp_notifier.go	39.63% <100.00%> (ø)
... and 19 more